Author Topic: As Good as a Header? (Read 8853 times)

Plainview · « **on:** May 30, 2017, 08:15:29 PM »

I've said before that the factory 4-into-2 manifold looks like a pretty darned efficient design to me. It effectively creates a Tri-Y header, which I'm sure is why they did it - to enhance low and midrange torque.

The bottleneck of course is where the two intermediate pipes join and become one little bitty pipe right before the catalytic converter.

So what do you think - is doing this going to produce results about as good as what a Tri-Y header would? Note, there's not converter in sight...

DSC_8214 by Will Baker, on Flickr

Oh, and it got a lot louder... LOL. Not really obnoxious, but definitely noticeable now.

OTO Phil · « **Reply #1 on:** May 30, 2017, 08:41:15 PM »

You'll notice some top end gain from the larger pipe, but the big gain is in the cam IMHO

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emsvitil · « **Reply #2 on:** May 30, 2017, 08:41:50 PM »

You could use a merge collector for the joining. Would be a bit smoother.

What kind of gain do you get with the longer 2 pipes (85 older) vs the short merge with the 86 + ?

I also think the connection of the manifold to the 2 downpipes could be made a bit smoother............

Plainview · « **Reply #3 on:** May 30, 2017, 08:59:38 PM »

Quote from: ExCabSwap on May 30, 2017, 08:41:15 PM

You'll notice some top end gain from the larger pipe, but the big gain is in the cam IMHO

Sent from my LG-H830 using Tapatalk

We could go into the discussion of how you can add all the airflow potential in the world but if the cam is small it won't make much difference. I definitely felt a bump in midrange power, from about 2600-4000 RPM. Above 4400 or so there's just not much there. At this point I assume that's the cam limiting things but the carb could have issues too.

The question is simply - with this mod will a header really be much advantage? I've removed the biggest bottlenecks in the stock system - that puny pipe the two intermediate pipes neck down into and the cat converter. So if I made no other changes (the engine is 100% stock), would a header buy me anything over this setup?

If I went to a little bit bigger cam, would a header be a significant advantage over this setup?

Quote from: emsvitil on May 30, 2017, 08:41:50 PM

You could use a merge collector for the joining. Would be a bit smoother.

What kind of gain do you get with the longer 2 pipes (85 older) vs the short merge with the 86 + ?

I also think the connection of the manifold to the 2 downpipes could be made a bit smoother............

Good question & observations. I'm sure a header would be more efficient. The question is - how much more efficient, and would it be worth the money spent? I'm talking about a comparable header, like a Thorley Tri-Y. A 4-tube header is a bit different animal.

I have no idea about the 86+ systems. I assume this 4-2-1 setup is probably better than a short runner manifold that is a 4-1 system, but that's just an assumption.

I'm feeling a noticeable boost in midrange power with this change. I'm guessing the factory cam is just not big enough to support any extra power production above ~4500 RPM where I don't feel much difference at all. Let's say I was to install a little bit bigger cam that could make power all the way to 5200-5500 RPM. At that point, how much would this setup be holding me back vs. a header?

emsvitil · « **Reply #4 on:** May 30, 2017, 09:39:21 PM »

I don't think a header is worth it........

The 86+ pipes merge right away after the manifold. Maybe 6" of dual pipe.

I know on the 86, the dual pipes insert into the manifold; I assume the 85 is the same........

There are 2 places in the stock system to smooth flow.

1. Where the 2 pipes insert into the manifold. If there's some way to make it so that the manifold inserted into downpipes instead........

2. This applies to the stock manifold and header: The late heads have the pear shaped exhaust the flows into a round port.
Need some way to make the exhaust port round to match the manifold or header.

Plainview · « **Reply #5 on:** May 30, 2017, 09:55:48 PM »

Quote from: emsvitil on May 30, 2017, 09:39:21 PM

I don't think a header is worth it........

The 86+ pipes merge right away after the manifold. Maybe 6" of dual pipe.

I know on the 86, the dual pipes insert into the manifold; I assume the 85 is the same........

Oh, I misunderstood. I thought the 86+ system was a 4-into-1 system. You're saying it's still 4-2-1 but the 2 intermediate pipes are much shorter. Hmmm... I really don't know but maybe that *is* a better setup? After all, the REs had a few more ponies than the Rs.

Quote from: emsvitil on May 30, 2017, 09:39:21 PM

There are 2 places in the stock system to smooth flow.

1. Where the 2 pipes insert into the manifold. If there's some way to make it so that the manifold inserted into downpipes instead........

2. This applies to the stock manifold and header: The late heads have the pear shaped exhaust the flows into a round port.
Need some way to make the exhaust port round to match the manifold or header.

If I end up taking the manifold off (I think it has a small leak so this may happen sooner than later) I'll take a good look at how it mates up to the intermediate pipes.

As for the exhaust ports, the 22R doesn't have those pear shaped ports.

As long as the round ports in the head are matched decently to the openings in the manifold, that should be a pretty efficient design.

emsvitil · « **Reply #6 on:** May 30, 2017, 10:07:02 PM »

I think the shorter pipes were for the IFS clearance, not better efficiency as I think the 85 22REs had the long pipes too.

I think the long pipes were for torque. Don't remember them on a 78 celica or 76 corona with a 20R, but do remember the long pipes on my friends early 70s truck with an 18R. They had to be worth something, because no doubt they were more expensive to make......

Are you early or late 84? I think the pear shaped ports started with the late (shorter block) 22R(E)s

Plainview · « **Reply #7 on:** May 30, 2017, 10:42:56 PM »

I have the early tall deck block - 22R. That was my understanding too, that the pear shaped port was an RE feature and one way to distinguish the RE heads from the Rs.

Makes sense why the design change for IFS. Hmmm...

But ya know, a lot of times things that were more expensive to make weren't necessarily better. Such is the nature of engineering. An engineer has a good idea, it goes to production, and later on it's determined that another, simpler idea works just as well if not better.

Eventually I'll put my 20R head on this engine. The hybrid motor I built for my standard cab has a lot more oomph than this stock engine, and I never got rid of that restriction where the intermediate pipes come together on that truck.

emsvitil · « **Reply #8 on:** May 30, 2017, 11:06:11 PM »

Here you can see the short pipes and the short section that goes into the manifold.

I think the flow improvements would be in the manifold/pipe interface as you're going from larger to smaller and NOT smoothly.....

emsvitil · « **Reply #9 on:** May 31, 2017, 02:11:39 AM »

What's the diameter of the 2 downpipes, then the diameter of the new section of pipe?

What I'd really like to know is what the joining of the cylinders (1,4 and 2,3) looks like inside the manifold............

Gnarly4X · « **Reply #10 on:** May 31, 2017, 03:07:49 AM »

Great discussion!

There’s lots of speculation and assumptions, and much of it makes sense in the descriptions.

I would be fun to see what the changes do on a chassis dyno.

I think it’s important to differentiate the modifications to a 22R and a 22RE. The exhaust and the DT header changes on my 1st 1986 22RE definitely were wrong – too big - and I lost very noticeable low end torque. I had the muffler changed, which helped. With that set up I gained some upper RPM power and but lost some off idle to about 2000 RPM torque.

With my stock 1985 22R, the DT header and larger tubing and free-flow muffler, and no cat made a very noticeable difference in low end torque and upper RPMs.

How did Toyota get the 20 HP gain from the 22R @ 96 HP to the 22RE @ 116 HP?

The Toyota engineers had 20 or 30 years to develop these legendary engines in their multi-million dollar “shop” so I believe the factory engines are very well engineered….. but they had to comply with legal restrictions while maintaining a degree of fuel efficiency and consumer perceived reliability. When I went looking for more torque, I wasn’t overly concerned with meeting the legal restrictions or fuel economy.

Plainview has opened up the always interesting discussion on what these modifications do and why. Again, I go back to the marketing hype (real or not?) by the aftermarket suppliers. There are lots of claims, BUT please show me some certified comparison dyno tests. I’m not saying that dyno tests are the end-all be-all, but at least they would provide some baseline data to have a more valid discussion.

That’s just my opinion – it may be worthless.

Gnarls.

Gnarly4X · « **Reply #11 on:** May 31, 2017, 03:45:46 AM »

Hey Plainview,

You mention "worth".... so cost per increase in numbers is typically always a consideration. How much have you spent on this exhaust system modification? I assume your local muffler shop did the work?

Is mandrel bent exhaust tubing done at a muffler shop and how much more is the cost?

Gnarls.

emsvitil · « **Reply #12 on:** May 31, 2017, 04:04:23 AM »

I think a lot of the gain of 22R to 22RE was the intake manifold.

From the short unequal length runners of the 22R to the long equal length runners on the 22RE

BTW, in 86 it was 103/133 HP/TQ vs 116/140 both @ 2800/4800 rpm

emsvitil · « **Reply #13 on:** May 31, 2017, 04:05:32 AM »

Gnarly,

What are the tube sizes on the DT header for comparison to stock tri-y manifold?

H8PVMNT · « **Reply #14 on:** May 31, 2017, 07:28:03 AM »

I can comment on this since I just experienced a before and after...

I recently swapped from the stock 22r manifold with double down pipe (ports were matched up and a 2 1/4" collector added at the end) to a NWOR tri-y header. After running a couple weeks with the header, pulling hills, bucking head winds, I think I can perceive a little seat of the pants gain from the header, but not huge.

I think that stock manifold with the double down pipe is actually a pretty good piece. Runners are very similar in length and size as my header. I'm sure the header is a bit smoother inside and probably has a bit more thought put into scavenging.

I all ready had my header in the shed from years ago. I would not go out and buy a header these days if I had the double down pipe stock setup.

Header sounds cooler though

.

Plainview · « **Reply #15 on:** May 31, 2017, 04:26:38 PM »

Quote from: emsvitil on May 30, 2017, 11:06:11 PM

Here you can see the short pipes and the short section that goes into the manifold.

I think the flow improvements would be in the manifold/pipe interface as you're going from larger to smaller and NOT smoothly.....

Interesting. First thing I notice in those pictures is that the single pipe that the two intermediate pipes dump into is considerably larger than the stock pipe on my truck and the transition is smoother. The single pipe on my truck between the intermediate pipes and the cat was literally about the same size as one single intermediate pipe, so that's a halving of the flow area and it's a short, abrupt transition. The setup in your pictures looks MUCH better in that regard, much more gradual transition to a pipe that is considerably larger than the intermediate pipes.

As to the joining of the intermediate pipes to the manifold - if the manifold has a recess to accomodate those short stubs and the passage inside the manifold has the same inside diameter as the ID of the intermediate pipes then the transition would be fairly smooth. Definitely something to look at.

Quote from: Gnarly4X on May 31, 2017, 03:45:46 AM

Hey Plainview,

You mention "worth".... so cost per increase in numbers is typically always a consideration. How much have you spent on this exhaust system modification? I assume your local muffler shop did the work?

Is mandrel bent exhaust tubing done at a muffler shop and how much more is the cost?

Gnarls.

There are shops around here that could do mandrel bends but I did this on the cheap so it's not the best system or the best work. Honestly, a 2.25" pipe is plenty big so the reductions in area at the bends probably don't offer much restriction. I think once the exhaust is past the intermediate pipes the main sources of restriction are past.

I would have had to do this work anyway if I'd gotten a header, so that's a sunk cost. The stock muffler was about to rust through and the pipes weren't far behind, so a new exhaust was needed regardless. The bigger pipe really didn't cost more than stock diameter pipe would have. The question is whether the several hundred dollars for a header at this point would be "worth it." IMO, if I'm only going to gain another few horsepower, the answer is no. As mentioned in an earlier post - my hybrid motor makes a lot more power than this engine and it didn't have this level of exhaust upgrade behind it. For the money a header would cost, I'd rather buy a new cam, adjustable gear, and put the 20R head in this truck. THAT would net me a much bigger increase in power.

Quote from: H8PVMNT on May 31, 2017, 07:28:03 AM

I can comment on this since I just experienced a before and after...

I recently swapped from the stock 22r manifold with double down pipe (ports were matched up and a 2 1/4" collector added at the end) to a NWOR tri-y header. After running a couple weeks with the header, pulling hills, bucking head winds, I think I can perceive a little seat of the pants gain from the header, but not huge.

I think that stock manifold with the double down pipe is actually a pretty good piece. Runners are very similar in length and size as my header. I'm sure the header is a bit smoother inside and probably has a bit more thought put into scavenging.

I all ready had my header in the shed from years ago. I would not go out and buy a header these days if I had the double down pipe stock setup.

Header sounds cooler though .

LOL... Your statement "...I think I can perceive a little seat of the pants gain..." tells me all I need to know. If the power improvement wasn't so immediately noticeable that you had to drive around awhile to "think" you gained a little then the cost of a header is definitely not worth it to me.

I do truly believe I've dealt with the major sources of restriction in this exhaust system and that any further improvements (header, mandrel bent pipe) would be a lot of money spent for very little gain, especially with a totally stock engine. If I wanted to run a big cam and high RPMs then those things might be something to consider. But, as it is, I just want to go a little bigger on the cam and gain some more power in the 2500-5000 RPM range. I fully understand that in order to do that I'll give up a little below 2500 but that's okay, and will be even more acceptable once I re-gear.

Great discussion folks, thanks for participating!

Gnarly4X · « **Reply #16 on:** May 31, 2017, 06:30:44 PM »

Quote from: Plainview on May 31, 2017, 04:26:38 PM

I.... Honestly, a 2.25" pipe is plenty big so the reductions in area at the bends probably don't offer much restriction. I think once the exhaust is past the intermediate pipes the main sources of restriction are past.

Hi Plainview... yes a very good discussion.

Just my opinion based on my research.... mandrel bends are considered by the exhaust systems experts a "measureable" difference over pressure bent pipe. The first pressure bend is the restriction and doesn't matter what's after it. There is more to the physics (flow dynamics) than just the restriction factor.. there is the turbulence and change in the velocity and sonic pressure wave caused by a pressure bent pipe.

Jumping on a highly touted camshaft profile with fractions of inches and very small degrees of change with the intent to increase volumetric efficiency then NOT completely considering the exhaust flow factor would seem like at the very least a badly overlooked design consideration. In terms of economics and power gain, why would you spend $1200 for a ported head with OS valves and a torquey cam, then skimp on your exhaust pipe?

How much more does it cost for 5 mandrel bends compared to the cost of 5 pressure bends?

Gnarls.

Prismo · « **Reply #17 on:** May 31, 2017, 09:27:14 PM »

Just make sure to anchor it to the transmission or the pipe WILL crack at the Y, ask me how I know lol

emsvitil · « **Reply #18 on:** May 31, 2017, 09:42:49 PM »

Quote from: Prismo on May 31, 2017, 09:27:14 PM

Just make sure to anchor it to the transmission or the pipe WILL crack at the Y, ask me how I know lol

I know........

Plainview · « **Reply #19 on:** May 31, 2017, 10:58:33 PM »

Quote from: Gnarly4X on May 31, 2017, 06:30:44 PM

Hi Plainview... yes a very good discussion.

Just my opinion based on my research.... mandrel bends are considered by the exhaust systems experts a "measureable" difference over pressure bent pipe. The first pressure bend is the restriction and doesn't matter what's after it. There is more to the physics (flow dynamics) than just the restriction factor.. there is the turbulence and change in the velocity and sonic pressure wave caused by a pressure bent pipe.

Jumping on a highly touted camshaft profile with fractions of inches and very small degrees of change with the intent to increase volumetric efficiency then NOT completely considering the exhaust flow factor would seem like at the very least a badly overlooked design consideration. In terms of economics and power gain, why would you spend $1200 for a ported head with OS valves and a torquey cam, then skimp on your exhaust pipe?

How much more does it cost for 5 mandrel bends compared to the cost of 5 pressure bends?

Gnarls.

Last question first: A lot. Especially when you consider the time investment in driving to a shop that will actually take the time to do this kind of work right. The shop that did the system on my truck is a Meineke close to my house and they did it quickly and cheaply. I was able to go enjoy a nice leisurely lunch and they had it done by the time I got back. It's not pretty, but it gets the job done and for a low price. It's certainly not the most efficient exhaust pipe I could have had installed, but that's not what I paid for.

Which leads to the next thing - pipe diameter plays a HUGE role here. Consider - put a 6" pipe on your truck. Do you really think a few compression bends would make *any* difference to your 125-140 horsepower (at best) engine? The smaller the pipe diameter the more critical it be bent efficiently.

A 2.25" pipe is plenty big for the engine in my truck. I don't know what the stock size pipe was, but 2.25" looks huge in comparison. So there's a few compression bends in it (and unnecessary welded joints) - it's still a major improvement over stock which is verified by the fact the truck is noticeably stronger in the midrange now. A 2.25" exhaust pipe can easily support 175 horsepower or more. Subtract some for compression bends and other inefficiencies and we're down to 150HP. Big deal. If you're really that concerned about it, put a 2.5" pipe on. If the header is designed right you won't lose low end performance with bigger pipe. I suppose a Tri-Y design might be more sensitive to this though...?

http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/#easy
there are a couple of things at that link that I've seen evidence to the contrary, but overall this is good tech.

Again it comes down to - how much power would the extra expense (including time investment) buy me? My feeling is "not much." The only shop I know of that would do mandrel bending, or properly assemble a system if your provided the bends is a 1/2 hour freeway drive from my house. Basically I'd flush most of a day getting that done and they would surely charge a lot more. But hey, you want to pay for a mandrel bent system on my truck, I'm accepting donations.

As to very small camshaft changes - they will make almost no real world difference so I don't stress out about them. One cam that has 2 more degrees duration and .010" more lift than another but the same lobe positions will in all likelihood perform the same. You might see the difference of a few HP at certain RPMs on a dyno but we don't drive dynos. I tend to think of cams in ranges of duration and always look to get the max lift I can for a given duration within the boundaries of what the head and valvetrain will allow. When I get around to reinstalling the 20R head I'm going to be looking at cams in the 208-216 @ .050" on the intake side duration range.

Mudder · « **Reply #20 on:** May 31, 2017, 11:05:59 PM »

Quote from: Prismo on May 31, 2017, 09:27:14 PM

Just make sure to anchor it to the transmission or the pipe WILL crack at the Y, ask me how I know lol

A few years back I learned that mistake the hard way as well. Driving down the freeway at 60 and my truck got extremely loud all of the sudden.

emsvitil · « **Reply #21 on:** Jun 01, 2017, 12:00:13 AM »

I weld up my own exhaust with sections of mandrel bend pipes....

As long as you're not getting the 'krinkle' bend, I've heard that you just go up to the next size pipe for a non-mandrel bent exhaust...........

Plainview · « **Reply #22 on:** Jun 01, 2017, 12:03:42 AM »

I hate people with welders and the knowledge of how to use them.

emsvitil · « **Reply #23 on:** Jun 01, 2017, 12:32:05 AM »

Hmmmmmmmm.........

http://www.mezporting.com/exhaust_length.html

Gnarly4X · « **Reply #24 on:** Jun 01, 2017, 04:20:03 AM »

Quote from: Plainview on May 31, 2017, 10:58:33 PM

Last question first: A lot. Especially when you consider the time investment in driving to a shop that will actually take the time to do this kind of work right. The shop that did the system on my truck is a Meineke close to my house and they did it quickly and cheaply. I was able to go enjoy a nice leisurely lunch and they had it done by the time I got back. It's not pretty, but it gets the job done and for a low price. It's certainly not the most efficient exhaust pipe I could have had installed, but that's not what I paid for.

Which leads to the next thing - pipe diameter plays a HUGE role here. Consider - put a 6" pipe on your truck. Do you really think a few compression bends would make *any* difference to your 125-140 horsepower (at best) engine? The smaller the pipe diameter the more critical it be bent efficiently.

A 2.25" pipe is plenty big for the engine in my truck. I don't know what the stock size pipe was, but 2.25" looks huge in comparison. So there's a few compression bends in it (and unnecessary welded joints) - it's still a major improvement over stock which is verified by the fact the truck is noticeably stronger in the midrange now. A 2.25" exhaust pipe can easily support 175 horsepower or more. Subtract some for compression bends and other inefficiencies and we're down to 150HP. Big deal. If you're really that concerned about it, put a 2.5" pipe on. If the header is designed right you won't lose low end performance with bigger pipe. I suppose a Tri-Y design might be more sensitive to this though...?

http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/#easy
there are a couple of things at that link that I've seen evidence to the contrary, but overall this is good tech.

Again it comes down to - how much power would the extra expense (including time investment) buy me? My feeling is "not much." The only shop I know of that would do mandrel bending, or properly assemble a system if your provided the bends is a 1/2 hour freeway drive from my house. Basically I'd flush most of a day getting that done and they would surely charge a lot more. But hey, you want to pay for a mandrel bent system on my truck, I'm accepting donations.

As to very small camshaft changes - they will make almost no real world difference so I don't stress out about them. One cam that has 2 more degrees duration and .010" more lift than another but the same lobe positions will in all likelihood perform the same. You might see the difference of a few HP at certain RPMs on a dyno but we don't drive dynos. I tend to think of cams in ranges of duration and always look to get the max lift I can for a given duration within the boundaries of what the head and valvetrain will allow. When I get around to reinstalling the 20R head I'm going to be looking at cams in the 208-216 @ .050" on the intake side duration range.

Hey Plainview,

I don’t disagree with anything you said there.

I certainly understand time and money. At 69 years of age I have strong opinions about how significant those two aspects of my life have been up to now.

First, I did not mean to imply that you didn’t consider the exhaust mods you’ve done in terms of performance gains, or that you were being a cheap-skate. Quite the contrary.

Right now most of this discussion, and many discussions like this, is just opinions, assumptions and speculation with some subjective butt-dyno mixed in.

How much difference would mandrel bends make in added flow in your engine?....you don’t know.

My point, which I didn’t make very well, was simply that starting from a stock 22, forward in the quest for more power, to all the modifications to add the torque number you want at a specific RPM range, begins and ends with incremental increases. Despite the claims and advertising, until I see a dyno sheet, I believe each mod - ported head, over-sized valves, hotter cam profile, over-bored cylinders, intake manifold and carb, increased compression ratio, and exhaust system – will only produce relatively small increases as separate and individual changes. But obviously for maximum performance gain, you look at each change that affects the engine’s volumetric efficiency as a “group” or package. However, I understand that many of us can and do only make single modifications – like header, pipe and muffler.

From my experience, those very small increments and changes were very noticeable (although not so much in my 22RE). H8PVMNT, and others, have clearly stated that in their posts.

When I started looking for more torque with my 96 HP 22R, I wanted to see if by just changing the camshaft would make any difference. It was basically a $100 to $200 bolt in. I already knew that the DT header (then was $225) and opened exhaust (approximately another $200) DID make a noticeable difference. I was actually looking for a small, but noticeable, amount of “cheap” torque.

And today, I’m still looking, and considering the cost of my recent engine rebuild in time and money may end up as you said:

“Again it comes down to - how much power would the extra expense (including time investment) buy me? My feeling is "not much."

By the way, I forgot to ask..... how many aftermarket performance exhaust systems that are NOT mandrel bent piping can you show me?

Gnarls.

Plainview · « **Reply #25 on:** Jun 10, 2017, 10:45:04 AM »

Well, I think this mod may have caused my carb to run lean at higher RPMs. At least that's the working theory at this point.

With the truck loaded down with all the stuff for an annual 4-day party in the woods I had to go down to 4th gear to maintain 55MPH going up Snoqualmie Pass (Eastbound). That had the engine running flat-out at 4100 RPM and it started to overheat. It cooled off as soon as I slowed down and I pulled off at the pass to give it a rest and check the water level (it was full). The needle never got into the red but it got right up to it and the engine is still running like it always has so I don't think I hurt anything.

There are other issues at play, the engine won't idle below 1000 RPM and it has a bit of a flutter (been doing this since I bought it) so I suspect a vacuum leak somewhere but that shouldn't affect WOT mixture enough to make a difference. I need to go through the carb and the distributor and make sure everything is working per factory specs before I can troubleshoot further but my gut tells me that freeing up the exhaust really increased airflow through the engine and the already lean factory tune is now too lean for best power and will cause it to run hot at WOT. Going to have to figure out what jets I have and see if I can get some bigger Hitachis in there.

Gnarly4X · « **Reply #26 on:** Jun 10, 2017, 06:58:43 PM »

Quote from: Plainview on Jun 10, 2017, 10:45:04 AM

Well, I think this mod may have caused my carb to run lean at higher RPMs. At least that's the working theory at this point.

Have you pulled the spark plugs?

Gnarls.

Plainview · « **Reply #27 on:** Jun 12, 2017, 03:58:06 PM »

Not yet. Thing about plug reading is that you need to do it right after whatever it is you're looking for occurs. Driving around town will color the plugs differently than that full power/full load pull up a long hill, so if you don't do it right then and there, there's not much point in doing it now. Of course, if the engine's running lean all the time the plugs will show that.

Gnarly4X · « **Reply #28 on:** Jun 12, 2017, 05:48:06 PM »

Quote from: Plainview on Jun 12, 2017, 03:58:06 PM

Not yet. Thing about plug reading is that you need to do it right after whatever it is you're looking for occurs. Driving around town will color the plugs differently than that full power/full load pull up a long hill, so if you don't do it right then and there, there's not much point in doing it now. Of course, if the engine's running lean all the time the plugs will show that.

I understand what you're saying. And, if you are a plug-reading guru and using just the spark plugs in a critical race tuning effort, I suppose you would want to get a clean view. But unless the engine is having a serious A/F issue, you should be able to get a decent idea whether or not your AF mixture is running lean or rich without pulling the plugs immediately after shutting down from a WOT drag strip run.

That's just my opinion - it may be worthless.

Gnarls

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