88' shelby Z quest for 11's (lots of pics)

[Shadow]

So that I dont lose my current mental model of how things work, help me understand this please:

The comparison I am making is that at 28psi on stock intake/head/cam/exh mani, stock gap worked fine.

Moparzrules build has a much higher flowing setup, but the problem is occuring at 18psi.

Looking at the dyno charts he posted, the output power is a little lower than the 28psi scenario, which was around 300hp.

So for this particular airflow comparison, ignoring AFR's for the moment, the airflow and cylinder pressures are unlikely to be vastly different, if anything, there was higher cylinder pressure in the 28psi configuration.

My point here is not to nitpick, but to suggest that there is currently no argument that spark plug gap has anything to with his issue, nor that spark plug gap plays an important role at 250hp to 300hp airflow/power levels given similar air charge temperatures.

So am I missing something? What is leading people to believe spark gap has anything to do with this issue?

And yes, its a very quick and easy thing to check and change, so I would still recommend doing it. I'm not saying its NOT the issue, I'm trying to get a clear grasp of what the logic is behind suggesting it is, because I dont see it.

All comments were made Before we knew what power the motor was making. (that's My Story and I'm Sticking to it!)

[moparzrule]

Well, how much power would you expect it to make at only 12psi? I think 236whp is pretty good, and you can clearly see it's still breaking up in the top end. The tune was just so far out, and it still is somewhat just a lot closer than before. Like I said it gained 45whp just by getting fuel in check and 10 degrees of timing. I believe it needs like 10 more degrees but for some reason I can't even run 15psi on pump gas without knock with that much timing. I know the knock sensor is working because once it threw the CEL I checked the plugs and sure enough it had the pepper on them.

Unless of course the 4 bar map is the issue. Borrowing a friends 3 bar map, and modifying the tables in shelgame's ''stage IV'' calibration for my 86lb injectors to find out.

[lengel]

Looking good Matt! Seems like good numbers for only 12lb! Get that breaking up issue taking care of and your good to go for Cecil next sat.

[OmniLuvr]

so have we tried closing the gap yet! no, seriously, did you? would a colder plug be better too? 236 hp is pretty dang good on a stock cam and 12 psi! your combo should be able to make more than the "super 60" combo #'s at 18 psi but with a stock cam! i hate to just keep "throwing" parts at it, but have you tried a "new" coil yet?

[moparzrule]

yes and yes.

It was already only .030 but I still closed it to .025. Why would I need colder than RN9YC??

[Ondonti]

so have we tried closing the gap yet! no, seriously, did you? would a colder plug be better too? 236 hp is pretty dang good on a stock cam and 12 psi! your combo should be able to make more than the "super 60" combo #'s at 18 psi but with a stock cam! i hate to just keep "throwing" parts at it, but have you tried a "new" coil yet?

I don't quite understand the anti gap change movement here. The point of dropping the gap is testing the ignition system. It does not mean you have to keep running a small gap but it allows you to test your ignition system. Nobody can feel a 'hint' of blowout so I don't accept the idea that because you can't feel it, you are not losing power. Dyno can see it.
-------------------------------------------------------

You changed too many things to really have a fair check (changing timing) on the plugs. Heavily retarded timing would technically happen at a higher cylinder pressure and be harder to jump the gap. The wavy dyno sheet does sound like spark blowout. Spark blowout can happen for a lot of reasons, too rich, lean, mistimed, or just weak spark. If nobody knows, the standard diagnosis for spark blowout is excessive plug gap, no matter how big someone elses gap is, your's is excessive for your ignition system.

Regarding the dyno, even if your cam etc is not optimal, I would bet your timing map is still not close considering how poorly it ran at first and how little time you got into it. Just a guess but getting knock at 4000 means you need to pull back there but that doesn't mean your timing at 5500+ can't keep rising. My stock camshaft 3.0 Duster with no turbo currently has a huge timing jump as RPMs rise towards 7k. Gains 12 degrees from 4500 to 7000 and it can probably eek higher if I put time into it. You can't really force more air in with your tune but you can make better use of it. Having a choke in your system sometimes is worse because your tune is not optimized for that "choke" and exaggerates the downfall of power.

yes and yes.

It was already only .030 but I still closed it to .025. Why would I need colder than RN9YC??

Better to regap to .020 and change nothing else. Do nothing to increase knock or other complicating factors. This is a test more so than a "modification." Think of it as ignition limp home mode. That said, a lot of fast cars run teenage gaps even with wasted spark ignition.

[OmniLuvr]

I don't quite understand the anti gap change movement here

i was joking and serious at the same time, i actually really had hoped that he would have dropped the gap 20 or teens as others suggested, quick, easy and free? sounded like a winner idea to me? i was just trying to give him a little pat on the back at the power he made, and before getting an answer about the gapping, also wanted to know if he had tried something else AFTER the gap procedure... but wasnt clear on the outcome.

Why would I need colder than RN9YC??

not sure, but was slightly worried about the octane choice/to boost pressure/to power output ratio. i was already splashing a gallon of race gas to 5 gal of 91 @ 18 psi with a stock swirl head and "stock" parts to make 200 ish hp and feel safe. not really comparable builds, but part of the reason im a g-head guy now, i feel safer with lower oct and higher boost pressures.

id like to know when you get the misfire, if you are just "misfiring" or also getting a backfire to go with it? leading me to believe spark is blowing out (or not sparking) and igniting the fuel afterwards through the exhaust like a 2 step would?

Just a guess but getting knock at 4000 means you need to pull back there but that doesn't mean your timing at 5500+ can't keep rising.

VERY GOOD POINT! as in timing shouldnt be retarded throughout the entire rpm range by that many degrees, just where it needs to be, like at peak torque output to reduce knock there? but im not really sure what he was doing with the timing, was it cal related or dizzy adjusted?

also, im not sure how important the small (and lack there of) quench area in the swirl head will relate to a detonation problem at a given amount of boost? i mean, we are in slightly uncharted territory with this super flowing intake? the #'s are fairly high for the small amount of boost and stock cam? is the air too turbulent?

there was a benefit from fuel, then timing changes, but after timing, did we try to add a little more fuel down low to help with combustion chamber cooling?

im not a "tuner" yet, but just trying to get idea of whats happening? im wondering if you were getting knock before it was reading on the sensor, were the plugs checked for detonation?

[moparzrule]

This isn't a stock swirl head. Several CC's have been taken out of the chamber, it's probably getting close to a stock G head chamber volume. It's also probably the reason I needed a lot more timing than the standard swirl head calibration. There were no signs of detonation on the plugs until the CEL went off indicating knock.

Lowered timing at 4k and gave more up top. Seemed to pull good until 6000rpm now, then it starts to break up there and I get knock. But no more knock from 4-6k. Think I might try to add even more timing up there.

[shadow88]

Did you unshroud the valves? Have you run a similar head before and found it needed a lot more timing due to the increased chamber volume?

[Ondonti]

i was joking and serious at the same time, i actually really had hoped that he would have dropped the gap 20 or teens as others suggested, quick, easy and free? sounded like a winner idea to me? i was just trying to give him a little pat on the back at the power he made, and before getting an answer about the gapping, also wanted to know if he had tried something else AFTER the gap procedure... but wasnt clear on the outcome.


id like to know when you get the misfire, if you are just "misfiring" or also getting a backfire to go with it? leading me to believe spark is blowing out (or not sparking) and igniting the fuel afterwards through the exhaust like a 2 step would?

I know where you were going, I was glad you were reiterating the point about regapping.

I would still regap the plugs down to at least .020. When everything is worked out, the gap can be increased. It hurts nothing when your car is already proven "not happy." Really, all it hurts in most turbo cars is daily driving response. This is why guys try to avoid low gaps, not because they are worried about power. I have some Nissan friends who ran teenage gaps but were always annoyed by some quirks that causes in normal driving (light load misfires from the plug slightly fuel fouling).

That is a good point about backfires. I didn't realize it but video once showed backfires from my car at night when suffering blowout. Pretty hard to tell unless blowout is so bad your face hits the steering wheel :P

[Ondonti]

This isn't a stock swirl head. Several CC's have been taken out of the chamber, it's probably getting close to a stock G head chamber volume. It's also probably the reason I needed a lot more timing than the standard swirl head calibration. There were no signs of detonation on the plugs until the CEL went off indicating knock.

Lowered timing at 4k and gave more up top. Seemed to pull good until 6000rpm now, then it starts to break up there and I get knock. But no more knock from 4-6k. Think I might try to add even more timing up there.

Did you just do this timing change yesterday or is this what you did on the dyno? I would keep timing exactly the same, drop plug gap severely, and see what happens. Change more than one thing and its hard to know what happened. I say this because its safer than adding timing and hoping the knock goes away.

BTW, I know its not T-M style, but if you have full control and you have traction problems on the street, you could always pull more timing at peak torque to help traction and then run a more aggressive yet safe tune for slicks etc. That would help in the lower gears but hurt high gears. I kinda prefer useless power.

[Shadow]

yes and yes.

It was already only .030 but I still closed it to .025. Why would I need colder than RN9YC??

Just an FYI, I continue to run the Champion RN9YC's in the Charger with Zero issues. (switch back and forth with NGK's but have seen no differences)

[moparzrule]

Picked up some Sunoco 260 gt fuel on my way home from work today. Pulls good to 6500 with no knock now, then it sees knock and starts breaking up at 6500. But then again, although rated at 100 octane the real motor octane is only 95. So it still could be lack of octane...sadly.

If it was ignition it would run worse with higher octane, so it's definitely not ignition.

Also, got the 3 bar map from my friend today. Will be testing that out probably tomorrow.

[turbovanman²]

Well that's good and bad news.

[acannell]

Picked up some Sunoco 260 gt fuel on my way home from work today. Pulls good to 6500 with no knock now, then it sees knock and starts breaking up at 6500. But then again, although rated at 100 octane the real motor octane is only 95. So it still could be lack of octane...sadly.

If it was ignition it would run worse with higher octane, so it's definitely not ignition.

Also, got the 3 bar map from my friend today. Will be testing that out probably tomorrow.

any chance we can hear the knock on a phone video or something? maybe someone would notice something that would help

do you have a laptop/mptune? might want to try datalogging and see what knock retard is doing...maybe only one cylinder is doing it and that would be a clue or???

[moparzrule]

Swap to a 3 bar map i have still to get a 4 bar map to work right in Dick`s charger it does the same thing put the 3 bar map and Cal in it worked perfect

I really owe you one man, thank you so much for suggesting this.

Swapped to a 3 bar and Shelgame's stage 3 cal modified for my injectors, like night and day. Wow, what a difference. Pulls hard to 7k now, no knock. Not sure whats wrong with the 4 bar cal. I have a guess though, because I made positively sure that my fueling was all exactly the same (up to 29 PSI instead of 44 PSI though of course) as the 4 bar cal and I'm .8 A/F leaner across the board. Idle, part throttle, and WOT throughout the entire RPM range it's exactly .8 leaner. Good thing I was running a hair rich at 11.2:1, I had tuned it in there assuming running leaner due to the cam swap. Now I'm dead on 12:1 at WOT so I have to add more fuel before swapping the cam. It's also fairly lean at idle now too a hair over 15 so it misses and carries on a lot.
So my guess is that the voltage scale must not be exactly the same as our 2 and 3 bar MAP's....which is weird, but must be true.

Turned boost up to 16-17 so far, butt dyno guesses ~280whp. WOOT, now I'm stoked for Saturday.

[bakes]

I not to sure what is wrong with the scaling to 4 bar but mabey shelgame can take a look at it Glad i was able to help
Let rob now there is a problem with this cal I didnt 2 years ago after all the trouble with boostgeeks 4 bar cal we just didnt have time back then with Dick 's stroke and all

[OmniLuvr]

it could have even been the sensor itself?

[moparzrule]

Nah, it's an Omni power sensor, one of the best on the market.

[Ondonti]

So is dwell time something people are messing with on their cals when scaling?

I am not sure about high octane fuel being more demanding on spark plugs for full combustion. Good quality moderate octane fuel should burn more completely at a lower temperature. Its formulated to burn more completely at a low temperature.