KNOCK KNOCK and high IDC's HELP

[laza101]

Hi guys,
I currently run a 16g (see mods in profile) and have not been able to get the knock count down on pump gas. I've tried running 18-19psi on 94 octane and I'm using like 83% duty cycle on 650cc's with a rewired walbro 255 @ 46psi base, yet I still get 20+ counts at top of third gear and timing goes to crap 10-15 degrees. I've tried turning my fuel pressure up but no significant changes, the engine actually runs rougher at WOT with higher fuel pressure. On 100 octane at full boost (20psi is all it's got) I get 0 knock. If I turn the boost down to 16psi it's ok on pump. Anyone have any idea what's going on? Is the knock caused by the turbo producing too much hot air? I have a PTE 50-trim on the way and feel that these injectors will not be big enough for pump gas given my situation. Any suggestions appreciated.

BTW no vacuum leaks last time I checked.

 

[talon1979]

For some reason my 16g wants to knock like crazy no matter how much fuel I give it if I run above 15psi on pump gas. I know of a few other people whose 16g's act this way. Maybe you should try turning your boost down to 16psi where you said it worked good, or invest in a FMIC. It may be possible that you are heat soaking even the supra smic w/ 18-19psi of boost on pump gas. A friend of mine is currently running a 57trim in stock injectors and 16psi and his car is pulling like a freight train. The 650cc injectors should be enough for a 50trim. I would imagine that just like you said, at 18-19psi the air coming out of your 16g is just too hot.

 

[NJGSX96]

What type of fuel control do you have other than an adjustable FPR? AFC? 46psi base FP is high and 83% IDC on 650cc injectors is a lot for a 16G. Sounds to me like you are running way too much fuel.

 

[kpt4321]

At 18-19 psi with the stock SMIC, you might just have todeal with turning your boost down.

With the SMIC, my car is faster at 16 psi then it is at 18. At 18, it simply requires too much fuel and too much timing retard to cope with the knock.

 

[laza101]

I HAVE A SUPRA SMIC, NOT STOCK. And I have a ram air tube that feeds the filter with ambient air temperature.

 

[kpt4321]

Have you verified that your base timing is correct?

 

[Violater101]

You can only get 20psi out of this turbo? You should be able to get alot more than that out of it. I seriously think its your Supra SMIC at higher boost levels.

 

[talon1979]

I am not a huge fan of the Supra SMIC. I still think that you could heat soak it fairly easy just like a stock smic.

 

[NJGSX96]

I don't think the Supra SMIC is an issue at the moment if his profile is correct... Ontario Canada is not in a heat wave, at least not that I know of.

What fuel control do you have other than an adjustable FPR? Do you have an AFC? You are running a 2G MAS... are the HC in? What else have you logged? O2 sensor? trims? O2 feedback? When you run 100 octane and 20psi, does timing get pulled? Any changes made when you used 100 octane?

 

[Violater101]

Originally posted by NJGSX96
When you run 100 octane and 20psi, does timing get pulled?

Originally posted by laza101
... On 100 octane at full boost (20psi is all it's got) I get 0 knock.

 

[laza101]

I am programming my own ecu for fuel and yes I use a 2g mas, but my injector size, fuel and timing maps are taken care of. On race gas I can maintain 20+ degrees of timing at full boost. My boost spikes to about 24 and goes down to 20 in third gear - 0 knock on 100 octane. I don't believe my supra intercooler is inefficient as the car ran well in hot weather. ONE ODD THING: When I had my 550's in, my car ran great in mild-to-warm weather but ran like crap in cold weather (below 40 degrees) - somewhat "rough" acceleration and felt slower. The 650's kind of improved that but something's definitely fishy. Do turbo's become inefficient if they're worn (5 years of use)?

My low fuel trim is 119%, mid is 108% and high is 99% which I haven't played with yet. I don't think I have any boost leaks though.

And yes I know I'm dumping in more fuel than I should, but it doesn't matter if I do, I still get knock on pump gas @ 18+psi. Trust me somethings wrong, my bro can almost keep up with me with just 2.5" exhaust, intake and boost controller ('92 tsi).

 

[98autogstspyder]

ever heard of rich knock??? Tuning is not what i am good at yet but the idea came to mind so i threw it out there.

Alot of people still run their stock sidemounts with 16g's down here in hot south florida and can do with 16 psi as their limit. he has an upgraded sidemount up in frozen canada which should be enough. plus he said he has routed something to dump even more cold air on to it. i dont think it is the intercooler causing the problems.


Tyler

 

[NJGSX96]

Originally posted by 98autogstspyder
ever heard of rich knock??? Tuning is not what i am good at yet but the idea came to mind so i threw it out there.

Exactly what I suggested days ago. Even if it isn't the answer, something to try.

Again, my vote goes to too much fuel. 46psi base is a touch high and 83% IDC on 650s on a 16G is a lot for only 18psi. I checked all of my old logs and on my 16G, 43psi base and 550s I saw 85-90% IDC at 22psi and pump. On my 20G and now PTE GT32E, I have base at 43psi and my 650s hit 85% at 21psi on pump on a very conservative tune.

Worth a shot.

 

[Darktalon92]

I have a similar issue. My 18g with 18.5psi, 550's and hacked 2gmas with 48psi fuel pressure and I'm getting 95% IDC? I also have a Supra smic. I have it tuned for now with 10counts of knock or so but it seems i need more fuel to keep the knock down. Since its cold out I am needing more fuel so come summer time I can lean it out a bit more, but for now I can up the fuel pressure to 49 maybe to lower my IDC.

 

[Darktalon92]

Laza, I leaned out my settings about 10% and got about 6-10counts, actually I had more like 15-18counts before. My IDC went down to 86-90%, but got ok timing, like 16-19. So with that said you might want to lean it out a lot. I leaned it out 3% and the knock stayed there,but then I leaned it out enough (7% more)that the knock went down a fair bit (where it is now), then leaned it out even more (3%)and the knock went way up to 26, much more than before so that was too much so i turned it back up 3%, its worth a try I suppose. Also noticed that my 02's are down to .82-.80, but 02's mean nothing.
Hope this helps ya out even a bit.