Above 30psi, it does indeed misfire. We change the plugs quite often. And it's on its 3rd set of ignition coils. The most boost we've run on our GT35 set-up was 27psi. It made 480-490whp but I think the ported head and intake manifold helped a bit.

Shiv

 

We'll get to the bottom of this somehow. I hope. Before utter frustration sets in.
Thanks for the "spirited" chat.

 

Easy way to get to the bottom of it would be to come to our shop with the problem. That is, running c16 and 30psi of boost. We don't have a drag strip in front of the shop but we can make do...

shiv

 

i will bring the beer

 

As long as it's not Smog's favorite-King Cobra 40...

 

I hear he's upgraded to Mad Dog

 

Fock y'all

 

With a Dynojet, yes. With a Dyno Dynamics, no. You didn't specify which and I assumed the former.


I don't need to think about it for a second to know that it will be in fact a 'big deal', especially if you are going to throw a huge turbo at it. How are you going to address major issues like fuel cut, injector rescaling (going to larger injectors I hope) and resetting the timing maps that will subsequently be out of sync when the injector pulses are telling the ECU it isn't under load when in fact it is? Think about it.

Going to a GT35 armed only with an safcii is like walking into a gun fight armed with a screwdriver. Anyway, follow whatever advice you feel best supports a positive, reliable experience, and good luck!

 

I ran an 11.9 @118 on a S-afc with my 3071r ,granny driving on the launch. I have an S-afc and even with my smaller turbo it is very hard and inconsistent to tune my car with my s-afc. I cannot mess with my timming. Only have the option of doing it with my Wideband and S-afc and hoping my boost controller stays at a set amount. My car is tuned pig rich at 10.8-11.0 now but ive had this setup for 3k miles now. I am about to try some new prototype ems called Element , like the Aem but better . S-afc is just not safe

 

Y the hate???........

king cobra or mad dog= More bounce for the ounce???? no?

 

I think tuning is possible with an SAFC and a big turbo, I wouldn't recommend it because its a huge limitation without having control over your timing you are certainly taking risks.. From a scaling point of view, bigger injectors generally means reducing MAF frequency which also effects fuel cut (Effectively raising it) Its an "old school DSM" trick.. You do have one major issue, reducing the MAF frequency indirectly ends up altering your timing, under lower loads, the ECU attempts to give "more timing" as much as 22 degrees and 8 degrees or more at peak boost, with a big turbo, that can end up being too much timing advance and can cause detonation or misfire in some cases..

Anything that alters MAF reading can have that affect, however if you can alter timing either directly, or through offsets, you can in turn adjust it back to where it needs to be.

The one issue you find is there's only a range of adjustment you have, at some point adhoc alterations of MAF frequencies will no longer give you desired results (Either they are too low, or out of range) and in turn you may not be able to adjust that.. Giant injectors over 1000cc's are a good example of that potential because you only have a range of adjustment, once your over 1000cc's you'd likely end up removing nearly 50% of the MAF signal to compensate, at the least you have no more useful adjustment, at the worst you end up triggering a MAF error due to being out of range for TPS and RPM (Honestly I've never seen that error in any application I've worked on though)

If you WANT to use an SAFC, use it for fine tuning a base flash.. the base flash can set your rev limits, injector scaling, desired timing and fuel curves appropriate for your desired base tune, eliminate fuel cut.. Then you can add your tune on top of that.. Better yet, if you want to retain the stock ECU, consider the UTEC or XEDE (Depending on your needs, your tuner, and what type of tuning style your most comfortable with)

 

Jack, check your PM's

Gil-superz

 

I'm going to be running 660cc injectors, so i'm not that worried about scaling. As for the exede and utec.... I might as well just get a standalone. Utec and exede are pretty much an safc with the ability to map timing. "Injector scaling" on a piggy back I would assume just does the same thing as the safc by tricking the ecu with the MAF signal. The stock ECU will attempt to advance timing and as soon as it detects knock it will back out. If I have a huge knock problem then I will probably just give in and change my management, but I'm already having that problem and I'm still on the stock turbo. It only happens under part throttle in high gears. The guy im tuning with doesn't seem to think 20 degrees of advance is that extreme. He pretty much said no matter what, it's hard to avoid knock on pump fuel. Also he said stock computers tend to be more consistent. He could be wrong, but I'll never know unless I try it. If I have excessive problems then I will switch, but until then I'll give it a shot.

 

It's a known trick that people have used on this engine for awhile to up the injector size to avoid fuel cut. As far as sync with timing maps go... the stock ecu works off of a knock sensor for that no matter what. Even stock it advances until it sees knock and then backs out, so I don't see a problem there.

 

Most piggybacks alter MAF signal, and scaling for injectors on a piggyback usually involve scaling the MAF signal. The UTEC is the exception however since it directly controls injectors and timing. There's enough information out there to make an educated decision once you decide what you want to do.