Some tuning questions.....

J

Jsup

Member
Here's what I'm doing....just for the hell of it.

Like I said, I want to see if my O2 sensor is operating correctly. Therefore, I am going to add an O2 bung on the driver's side, for a total of 3 in the car. One in each collector and a third one on the driver's side right behind the one in the collector.

This new bung will hold a wideband O2. So I will have 2 wide bands, one on each side of the motor AND the heated stock unit.

I'm going to run the car to see if the stock unit is sending the ECU the correct information and get a feel as to where I stand.

My goal is to see if there is a discrepancy between the stock O2 and the wideband. If there isn't, then I have to see if there is a discrepancy between the two widebands.

I want to have an idea of where I sit and see if I have a good starting point.
 
I'm back...I went to TTP performance, worked with Matt and his guys, they were fantastic. Matt told me "I've never seen him so excited doing a dyno pull"...talking about my car. He strapped it down with four straps in back, he usually uses two. The car walked sideways on the dyno, he really enjoyed that. He said to me when I left "that's one sick C4"...they do a ton of C5/6 work there. It was a good afternoon.

here's some of the results. The RED LED AFR meter is on the passenger side, the one on the dyno screen is on the drivers side. To recap, the wideband I was using was on the passenger side, and it was reading lean. Yet the ECU was trying to pull fuel out.

You can see the passenger side is lean, and after we hit 4500 RMPs, it goes very rich. down to 10.0, which is as low as the meters will read.

Following is some pictures of the two side by side.

352310259.jpg


352310250.jpg


352310246.jpg


352310243.jpg


352310240.jpg


352310233.jpg
 
try to get the air/fuel ratio to run at about 14.5:1-14.7:1 at idle and up to about 2500rpm... than have it transition smoothly too a f/a ratio of about 12.7:1-13:1 above that rpm level and I think you'll find the power curve becomes far more consistent and impressive!
your running so LEAN at 17:1 and 18:1 IM surprised your not burning a piston and getting into detonation and busting a ring!

http://www.innovatemotorsports.com/products/lm1.php

hese scanners below are popular,
but WITHOUT BOTH A SCANNER AND A FACTORY SHOP MANUAL YOULL WASTE A GREAT DEAL OF TIME

viewtopic.php?f=50&t=609

http://www.harborfreight.com/cpi/ctaf/d ... mber=98614

this is what I use

http://www.etoolcart.com/autoxray-scann ... x6000.aspx

viewtopic.php?f=44&t=469&p=6061&hilit=scanner#p6061

tools you really need
SHOP MANUAL
timing light
vacuum gauge
IR temp gun
degree wheel
dial indicator and stand
fuel pressure gauge
V.O.M. meter
torque wrench
magnifying spark plug reader
lift or (4) 12 ton jack stands
basic mechanic hand tools
floor jack


90% of your problems will be found just running thru the check list and following the shop manual suggestions, yes diagnostic software , and owning a scanner is a very good idea!
 
grumpyvette said:
try to get the air/fuel ratio to run at about 14.5:1-14.7:1 at idle and up to about 2500rpm... than have it transition smoothly too a f/a ratio of about 12.7:1-13:1 above that rpm level and I think youll find the power curve becomes far more consistant and impressive!
your running so LEAN at 17:1 and 18:1 IM surprised your not burning a piston and getting into detonation and busting a ring!
Click to expand...

That 17/18:1 you see is VERY VERY brief. Once I hit 3000 RPMs it goes very rich.

OH, and some tibits I completely forgot about, since it wasn't my main purpose for being there.

1. The motor makes power clear through 6250 RPMs, where it doesn't drop off big, but just gently slopes down.
2. The motor starts making power in a big way around 2500 and sits pretty flat to 6250.
3. The trans shifts at 6400 RPMs, PERFECT according to Matt at TTP, a couple hundred off of peak is right where you want it. I got lucky at that one. I had to move the rev limiter up to 6700 RPMs because it hit the rev limiter before it was able to shift.
4. The Torque converter sits at 3000 RPMs and is perfect for the torque curve of the motor and shift points.

So some good did come out of the visit.

Before I mention what the number were, we believe there's at least 50HP left in the tune. Do you believe that?
 
"Before I mention what the number were, we believe there's at least 50HP left in the tune. Do you believe that?"


I don.t remember your exact engine combo, as I answer dozens of questions daily, and without a clear reference to look back at things get a bit blurred in my memory occasionally, but you could easily gain 5%-10% in a decent tune up and adjusting the ignition curve and fuel air ratios, Ive seen extreme cases where some guys found problems and corrected them and had results far exceeding that percentage, I know one guy whose 429 ford picked up well over 120hp when he removed partly clogged cats that the dyno showed were a huge restriction, as he was noseing over on the power after 3500rpm, test showed 6 psi of back pressure in one cat and 4 in the other

http://www.centuryperformance.com/tunin ... g-148.html

http://www.secondchancegarage.com/public/186.cfm

http://www.barrygrant.com/fromBarryGran ... ual-08.pdf

viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152

http://www.corvette-101.com/
(info on left border)

heres a couple darn good links you need to read thru, lets have some additional info or comments and questions??
 
grumpyvette said:
"Before I mention what the number were, we believe there's at least 50HP left in the tune. Do you believe that?"


I don.t remember your exact engine combo, as I answer dozens of questions daily, and without a clear referance to look back at things get a bit blured in my memory occasionally, but you could easily gain 5%-10% in a decent tune up and adjusting the ignition curve and fuel air ratios, Ive seen extreme cases where some guys found problems and corrected them and had results far exceeding that percentage, I know one guy whose 429 ford picked up well over 120hp when he removed partly clogged cats that the dyno showed were a huge restriction, as he was noseing over on the power after 3500rpm, test showed 6 psi of back pressure in one cat and 4 in the other
Click to expand...

That would be fine.

So what do you think? This is a stock ECU with a batch fire system. The AFR is the same at idle, up to about 2400-2800 only a 400 RPM gap. THEN the passenger side goes lean, then, comes back about 3000 RPMs to match the other side.

At first I thought maybe a leak off the headers? But then there would be a difference all the way up, wouldn't it be?

THEN I thought perhaps a bad injector not spraying correctly, but it works fine at high RPMS, they march

Then I am thinking maybe a spark plug went bad? IDK....

What should I be looking for? Again, this is BATCH FIRE and the two sides of the motor don't line up....any suggestions?

It can't all be in the tune, wouldn't both sides be equally bad if it were in the tune? I'm at a loss.
 
if the problems consistant you should be able to isolate and correct the problem thru testing or swapping parts from one side to the other in some cases or other testing and verifying clearances, etc,
a badly adjusted valve, a weak valve spring, a slightly clogged injector, a worn cam lobe, a partly clogged cat, a bad spark plug, a busted ring, a high resistance plug wire ,the list is almost endless, without being there and going thru a check list its going to be just guessing,
but ID sure start with a leakdown test, verifying the fuel pressure remains steady, and do a tune-up with new ignition components (plugs,cap, etc, test the ignition wire ,ID throw two differant brands of injector cleaner in a new tank of high test gas,Id check the injector wiring, etc.)and setting the ignition curve and look thru the shop manual, ID grab my infrared temp gun and take readings on all cylinders and ID read the plugs, and Id do a back pressure test on the exhaust, you might be surprised at the clues you might find.

heres a generic list but it might give you a clue or idea

viewtopic.php?f=50&t=609

viewtopic.php?f=50&t=874

viewtopic.php?f=50&t=671

viewtopic.php?f=44&t=773

viewtopic.php?f=50&t=785

viewtopic.php?f=44&t=579&p=743&hilit=infrared#p743
 
grumpyvette said:
if the problems consistant you should be able to isolate and correct the problem thru testing or swapping parts from one side to the other in some cases or other testing and verifying clearances, etc,
a badly adjusted valve, a weak valve spring, a slightly clogged injector, a worn cam lobe, a partly clogged cat, a bad spark plug, a busted ring, a high resistance plug wire ,the list is almost endless, without being there and going thru a check list its going to be just guessing,
but ID sure start with a leakdown test, verifying the fuel pressure remains steady, and do a tune-up with new ignition components (plugs,cap, etc, test the ignition wire ,ID throw two differant brands of injector cleaner in a new tank of high test gas,Id check the injector wiring, etc.)and setting the ignition curve and look thru the shop manual

heres a genaric list but it might give you a clue or idea

viewtopic.php?f=50&t=609
Click to expand...

Already did the cap, rotor, wires, plugs.

I will do a leakdown test. I have to get my hands on a gauge. I don't have one at my fingertips.

I'll swap the injectors from left to right, all 4, and see what happens.

The fuel pressure is steady, new high volume pump.
 
darn your fast I didn,t even finish posting :D :D guess IM going to be forced to learn how to type with more than one or two fingers :mrgreen:
 
grumpyvette said:
if the problems consistant you should be able to isolate and correct the problem thru testing or swapping parts from one side to the other in some cases or other testing and verifying clearances, etc,
a badly adjusted valve, a weak valve spring, a slightly clogged injector, a worn cam lobe, a partly clogged cat, a bad spark plug, a busted ring, a high resistance plug wire ,the list is almost endless, without being there and going thru a check list its going to be just guessing,
but ID sure start with a leakdown test, verifying the fuel pressure remains steady, and do a tune-up with new ignition components (plugs,cap, etc, test the ignition wire ,ID throw two differant brands of injector cleaner in a new tank of high test gas,Id check the injector wiring, etc.)and setting the ignition curve and look thru the shop manual, ID grab my infrared temp gun and take readings on all cylinders and ID read the plugs, and Id do a back pressure test on the exhaust, you might be surprised at the clues you might find.

heres a generic list but it might give you a clue or idea

viewtopic.php?f=50&t=609

viewtopic.php?f=50&t=874

viewtopic.php?f=50&t=671

viewtopic.php?f=44&t=773

viewtopic.php?f=50&t=785

viewtopic.php?f=44&t=579&p=743&hilit=infrared#p743
Click to expand...

OK Grumpy now you got me a bit nervous. It's a roller cam, built by Bullet. It's kinda hard to waste a roller cam.

Also, the issue is that it's ONLY at particular RPMs. 2400-2800. If it were a badly adjusted valve, wouldn't it be badly adjusted ALL THE TIME? Does the fact that outside that narrow RPM range, it goes RICH mean anything? If it were mechanical failure, such as cracked ring, why is it ONLY at that narrow operating range?

That's what I'm having the problem understanding.
 
not being there.not hearing it run, and not having access to all the info makes trouble shooting rather difficult over a computer.
if its only occuring in a narrow rpm band its probably ignition related or software controling the injectors, possiably fuel supply related, but thats very unlikely.
my guess would be the software controlling the injector pulse duration needs tweaking.
again, ideal idles at about 14.7:1 and stays near there untill about 2500-2800rpm then transitions to a 12.7-13:1 f/a ratio above 3000rpm, its no big deal if it gets as rich as 12.5:1 in some places along the rpm band but thats what you want to try to maintain( a 12.7-13:1 f/a ratio )
Your saying your dipping as rich as 10:1 that can frequently cause plug fouling and ignition problems if it hold that ratio for long
 
GREAT PHOTOS!!
far clearer than most that get posted!
BTW did you swap/test injectors??

YOUR plugs show your close to correct but almost every plug indicates slightly higher than ideal heat and a mild lean condition, ID suspect the software needs to be tweaked to richen the AVERAGE a/f ratio, (LONGER PULSE DURRATION ? LARGER INJECTORS?) or the coolant or air temp heat sensors are reading cooler that reality,you might try retarding the ignition advace curve rate and the total advance just a bit,also as the heat band on the plug ground indicates the plugs a bit hotter than ideal.
naturally you won,t use JUST that info, but its a good indicator, WHATS YOUR FEELINGS ON THIS?

http://www.4secondsflat.com/plug_chart.html
(#23)

viewtopic.php?f=70&t=202
 
grumpyvette said:
GREAT PHOTOS!!
far clearer than most that get posted!
BTW did you swap/test injectors??

YOUR plugs show your close to correct but almost every plug indicates slightly higher than ideal heat and a mild lean condition, ID suspect the software needs to be tweaked to richen the AVERAGE a/f ratio, (LONGER PULSE DURRATION ? LARGER INJECTORS?) or the coolant or air temp heat sensors are reading cooler that reality,you might try retarding the ignition advace curve rate and the total advance just a bit,also as the heat band on the plug ground indicates the plugs a bit hotter than ideal.
naturally you won,t use JUST that info, but its a good indicator, WHATS YOUR FEELINGS ON THIS?

http://www.4secondsflat.com/plug_chart.html
(#23)

viewtopic.php?f=70&t=202
Click to expand...

On that chart I think I'm about number 19. Now, this is a 5 heat range NGK Iridium plugs. Perhaps I can knock the plugs down a heat range, I may do that. I have to put plugs back in no matter what I do. Those plugs ain't cheap though. Sucks to have to replace them.

I am working with only 1.5 hands. My finger is still immobile from a car accident, and will be for the foreseeable future, EVERYTHING takes me longer than it should. Tell ya what, with the finger condition I really learned to use box wrenches, extensions, and swivels to get the plugs out today. Good thing I have years of work which resulted in a bunch of oddball tools to reach into places I can't get to easily. I did not get to switch the injectors today. Hopefully I'll get the cooler plugs and swap them in tomorrow, swap the injectors, and fire it up.

What's your thought on one heat range cooler? I'm thinking that's what I should do.

I'm thinking I'm knocking the plugs down two heat range levels, if they come up too cool, I know the one in the middle is the ticket.
 
I think your closer to #22-#23 , one of the important indications is the heat band stripe location on the ground electrode, yours is located almost back to the body threads, keep in mind much of the ash discoloration takes a good deal of time to build up and those are rather new or low mileage plugs that the ash has not had a great deal of time to build up on.
 
grumpyvette said:
I think your closer to #22-#23 , one of the important indications is the heat band stripe location on the ground electrode, yours is located almost back to the body threads, keep in mind much of the ash discoloration takes a good deal of time to build up and those are rather new or low mileage plugs that the ash has not had a great deal of time to build up on.
Click to expand...

What do you think of kicking it back two heat ranges?
 
not much to loose by trying that,
but I think ID also try a test of limiting the total ignition advance to 2 degrees less, first, and try that!
 
grumpyvette said:
not much to loose by trying that,
but I think ID also try a test of limiting the total ignition advance to 2 degrees less, first, and try that!
Click to expand...
I have to reinstall plugs, so I was going to do that with the cooler plugs, no more work there. THEN I'll try to knock back the timing. Just an issue of ease, not correctness.

I also validated the valve adjustment on the passenger side.

I got the injectors swapped from left to right. Stores are closed here on Sunday, I'll pick up and install the plugs tomorrow.

Then I'll roll back the timing, then do the vacuum thing we discussed.

any time,If a symtom comes and goes, rather at random, ID start looking at the plugs for indications of whats going on in the cylinders. ID do a compression/leak down test to verify its not mechanical in nature, Id verify the fuel pressure was consistant, Id open the carb and check internally for crud or broken parts, Id check the float levels and set the idle adjustemts and if I had a F/A meter ID be using it, to look for indications, and Id use a timing light to verify the timing curve advance runs smoothly, a VOM to do a few checks on voltage and resistance on ignition components , like plug wires and check the battery voltage bunder load,and and Id use an IR temp gun to verify the exhaust temp is reasonably consistant between cylinders as the first checks, you can,t cure the problem untill its isolated and clearly defined


when the leakdown test is done correctly results normally fall in the 2%-15% range and if testing shows 35% -100% its usually indicating a broken ring, burnt valve, bad head gasket, or a detonation damaged piston,etc. now if the piston was not at tdc, or a valve might be badly adjusted because the guy didn,t bother to lock the engines rotation durring the testing or remove the rocker tension, results are going to be suspect.
heating the engine up by running it prior to testing seems to help the test results slightly but it makes working on the engine durring testing a huge P.I.T.A. so its rarely done.
squirting some 20w50 oil into a cylinderthat testsed badly, than re-testing that cylinder will generally give you some indication of the leaks source if the results change because oil will tend to seal rings boosting results but not valves
 
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