Turbo Spark plug gap

[yeyo_racing]

What spark plug gap are you guys running for 8psi on a 2.8 turbo? My engine it's cutting off past 5k rpm and I think it's the plugs.

ECM has been chiped for 2bar map by Sinister, has MSD 6a box and MSD coil, cap and rotor and Magnecor wires. New module, new pickup, stock timing. Running 1 range colder Autolite plugs (number 23) @ .34

The engine was tuned on a dyno with BEGI FMU and Apexi but haven't been able to go past 5k ish

It feels as and ECM cut off but it isn't cuz it's kinda gradual. It's making full boost @ 3500 and keeps on going hard until it reaches 5K and starts to feel slower then around 5200 to 5300 rpms it cuts off.

[AaronGTR]

I think the problem is the plugs too, but not the gap. Get rid of those autolites, they are garbage! Especially on a boosted car. Get some NGK coppers or iridium tips. That might solve your problem right there. I always recommend running the stock gap to start off and see what it does. You want the run the most gap you can without misfiring so the spark gets better exposure to the air/fuel mix. If you change the plugs and it's still misfiring at .055", trying lowering the gap .005 at a time until it goes away. I wouldn't want to run lower than .035" really. If you have to go that small, then you aren't getting enough power to the plug.

[yeyo_racing]

I tuned the engine with UR5 and gap set @ .40 when it first showed the issue. I changed to Autolites # 23 for colder and went down to .34 gap, same issue.

I will stick with the Autolites for now since I can't seem to find UR6 anywhere here. BTW UR5 were running kinda hot thus why I changed to the ONLY colder plug I was able to find (Autolites). The interesting thing is that I gave the NGK part number @ Autozone and got Autolites Coppers.

I doubt is power to the plugs. I have MSD everything, see->

has MSD 6a box and MSD coil, cap and rotor and Magnecor wires. New module, new pickup, stock timing.

[SappySE107]

Post a datalog. Id like to see what the computer is doing.

[Mars]

Delco R42LTS @ 0.028"
Any larger on the gap and I can't pull 7000RPM. @ 11 - 12 psi supercharged intercooled.

I've noticed no ill effects from having the gap that small. It idles great and everything.

[RedZMonte]

im running NGK's at .035" gap on 7psi without problems.

[yeyo_racing]

Ben,

Here's the datalog I took yesterday night with the plugs set @ .25. I noticed the engine was having difficulties going past 5000 rpms.

2.8_turbo_LOG.xls

The almost WOT runs are highlited in yellow. I say almost cuz I was pressing the peddal from 1/2 to 3/4 since I did not notice any difference from 3/4 to WOT. Also, did a spark plug read on the NGK UR5 that I used for tunning the engine and it seems I'm running too much timing under boost. The color change on the ground strap is at the base and not on the apex.

I followed this tech article http://www.4secondsflat.com...rk_plug_reading.html

[SappySE107]

Battery voltage gets in the 11s, BLMs are very low, INT is crazy low, the advance is really low (and you highlighted a segment in the 20% TPS range). looks like the map kpa is halfed to make the 2 bar work.

I would say you need a better tune.

[bszopi]

Is battery voltage in the 11s while the car is running?! If so, that might explain why you are getting crappy spark irregardless of your components.

[SappySE107]

At lower RPM/Idle, yes. It goes back into the 12s and 13s with RPM.

[bszopi]

Still seems lower than it should be...

[yeyo_racing]

Yeah the charging thing is going to get addressed. It's due to the ASP crank pulley, I just received the small Over Drive pulley for the alt.

Ben, could the BLM and INT be affected by changes done via the SAFC? How much timing should have?

Thanks for your input guys, I really appreciate it.

[SappySE107]

It is, hence why I mentioned it. The voltage shouldn't throw the tune off that much (90 blm 50 int) but who knows. Start with voltage, but I still say the tune is way off.

[SappySE107]

Timing I cannot say for sure but 4 is not acceptable. Tuning is done in the computer, so anything you are doing to trick it is not helping, at all.

[yeyo_racing]

Tuning is done in the computer, so anything you are doing to trick it is not helping, at all.

Ben,

You are correct. I've been talking to another forum member in RFT (Shaun Hammitt) about this issue and he is 100% sure it's the APEXi causing havoc. If i put more fuel through the APEXi the ECM will pull timing and if I take out fuel it will add timing. He ran into the same problem himself with his turbo setup.

With that said, here are my options so far:

1- Talk to Ryan and have him burn me a new chip for the spare 315cc injectors I have and datalog till never end to have new chips burned and dialed in.
2- Sell the APEXi and a couple of things I don't need anymore and buy me and Ostrich and tune the car myself. I already downloaded TunerPro and the necessary files.
3- Do more selling and buy me a MegaSquirt
4- Sell an arm and a leg and buy me a Haltech

I am more inclined on the second option since it will cost me almost the same as having Ryan burn me a chip, not to mention I get to retain all of the basic functions GM put into it. However this is unkown territory for me and thus I will probably need assitance from you, Superdave and all other forum members with GM DIY tunning experience.

BTW, the alternator problem is fixed and that was not causing the incredibly low timing problems.

Any input will be greatly appreciatted. Thanks!