Anyone running a stock ecm with a turbocharger? I plan on upgrading to Accel DFI or FAST eventually but I want to know if I can use my stock ECM for the time being?

 

You can always install the 749 ECM. It works with boost.

 

You can with a FMU (fuel management unit). It bumps up the fuel pressure with boost.

 

Costom chips??

 

I'm currently running the stock 730 Speed Density TPI ECM with my Vortech S-Trim V1 supercharger. I'm also running a Vortech FMU and a secondary Vortech fuel pump. Maybe my setup is just messed up, but I'm really not happy with it at all. I've checked my FMU and supposedly it is setup properly (according to Vortech I'm running the correct washer), but the car never makes the same ammount of power every time I go WOT. Sometimes there is alot of power, sometimes very little. I dont have a Wideband 02 yet (or a fuel pressure guage) so I'm not 100% positive its a result of bad tuning on part of the FMU. But I have to say that I'm no longer a fan of FMU's after seeing how they are adjusted. I have no real sense of tuning, just whatever the box does when I change the washer thickness. I would rather convert to a completely electrical setup that can actually be fine tuned for the best performance and work with one big pump instead of two smaller pumps. I will be installing a 749 (sy/ty) ECM soon. I got one out of a wrecked 92 Syclone. Yes you do need a custom chip programmed for your V8. I will be using Tunercat R_T and the $58 definition file. IMHO this is the best DIY solution using the GM equipment when you need to work with boost. The FMU route would work with the right troubleshooting tools/guages, but for me personally, I just dont like it.

 

CrazyH, what ratio fmu and how much boost are you running?

 

I'm running the 8:1 black unit with 24 lb/hr injectors. I run between 6 and 7 psi, but not sure exactly how much (maybe 6.5psi?). I need to get a fual pressure guage and a WB02 setup with A/F ratio guage to see if my problem is the result of the FMU, but I dont feel the tranny slipping and my rearend is fine. It could possibly be a fuel issue too. This is unrelated to the problem I was talking about in that other thread regarding my powerband. Sometimes the car is a beast, sometimes its a dog. I hate that feeling when you stop accelerating ...

EDIT: Just a note to Darklord, Vortech also sells an adjustable FMU called the Super FMU (SFMU). This FMU can be somewhat tuned, but IMO not to the degree of the 749 ECM options. The FMU vs 749 Swap decesion comes down to weather you want a single GM package running the car with electronic adjustments, or multiple packages dealing with 3rd party parts and mechanical adjustments. Up to you.

 

I know that this is an unpopular opinion here, but an FMU does exactly what you tell it to do, nothing more, nothing less. If you are having tuning issues it’s not very likely that the fmu is doing something different every time, it’s difficult to build a simple mechanical device that acts even semi randomly, it will do what the design and installation causes it to do. The big problem with FMU’s is that they don’t start enriching the mixture till you’re at a higher boost level. That is actually helpful on a MAF car since at low boosts the MAF will detect the extra airflow and the mixture will be enriched by the ecm. It’s a bit of a hassle on a SD car since that just means that you have to run the top end just that much richer to keep the middle from being too lean. In the end, you’re always stuck with it going slightly lean in the midrange and rich at to top end unless you go slightly large on the FMU ratio and then bleed of the top of the range. Is that right? No, but it can be made more then good enough.

With that said, if you have an 8:1 FMU, base FP of 43psi and you’re seeing 6psi boost… well the FMU will be trying to give you 48psi fuel pressure, but the boost acting on the FPR will be ‘calling for’ 49psi, so the FMU isn’t doing anything. I’m guessing that with the slightly larger injectors you’re probably running rich at idle and part throttle and lean up top because you don’t have any fuel enrichment going on.