Vortech FMU, opinions?
04-12-2009, 03:15 PM
#1
0.5 BAR
Thread Starter
Join Date: Nov 2008
Posts: 166
Vortech FMU, opinions?
I've got a 1990 BMW 525i. 2.5l inline 6 with an auto tranny. 181hp of fury. Well the car is just too slow for what I want, so I'm considering turbocharging it HMT style (Meaning on a budget). Well there really is no economical way to tune these cars, so I've been thinking about a RR-FPR like the FMUs from Vortech. They are cheap and very widely used, but I've never believed in them because the amount of fuel needed, and the boost pressure, is not a linear relationship. But to get the AFRs in a safe range, I think it could be acceptable, so long as it doesn't vary by over a point or so. I'm fine with anything between 11-12.5. And being a low boost project (8psi A/A intercooled), I think it could work.
So, from those who have used these, care to share some opinions based on experience? Did it work? How accurate was it? What were your complaints?
Thanks!
So, from those who have used these, care to share some opinions based on experience? Did it work? How accurate was it? What were your complaints?
Thanks!
04-12-2009, 06:49 PM
#3
1.5 BAR
Join Date: Nov 2004
Posts: 820
The good 'ol fmu....as always the best choice is a means of tuning fuel and timing but that is not always possible. I have had personal experience with fmu's good and bad, so heres the deal:
you can run into problems with sky high fuel pressure popping fuel lines, so the solution to that is to make sure your under hood fuel lines that are rubber are all new and clamped well.
more than likely your stock fuel pump won't be able to keep up with the demands of the fmu, if walbro makes a 255 HIGH PRESSURE pump for your car then get that, if not, you need to supplement the stock pump with an in line (out of tank) pump.
The most dangerous situation with an fmu is boost transition, and part throttle boosting, in full throttle after the fuel pressure has shot up, fmu's do a good job of making the AFR rich usually like 11:1 (which is fine for your motor because it has fairly high compression at 10.5:1)
I would suggest retarding timing as well by at least a few degrees any way possible, but if you have good fuel lines, the proper fuel pump, and you try not to play with part throttle boosting to much an fmu WILL work for a low boost set up, I have seen it work many times.
A lot of people that have hesitation or jerking problems when they use an fmu don't realize that it's because they have not done a good enough job blocking boost pressure from the map sensor, or they have a stock fuel pump with no in line to back it up, and most stock pumps can't keep up with an fmu's demands.
you can run into problems with sky high fuel pressure popping fuel lines, so the solution to that is to make sure your under hood fuel lines that are rubber are all new and clamped well.
more than likely your stock fuel pump won't be able to keep up with the demands of the fmu, if walbro makes a 255 HIGH PRESSURE pump for your car then get that, if not, you need to supplement the stock pump with an in line (out of tank) pump.
The most dangerous situation with an fmu is boost transition, and part throttle boosting, in full throttle after the fuel pressure has shot up, fmu's do a good job of making the AFR rich usually like 11:1 (which is fine for your motor because it has fairly high compression at 10.5:1)
I would suggest retarding timing as well by at least a few degrees any way possible, but if you have good fuel lines, the proper fuel pump, and you try not to play with part throttle boosting to much an fmu WILL work for a low boost set up, I have seen it work many times.
A lot of people that have hesitation or jerking problems when they use an fmu don't realize that it's because they have not done a good enough job blocking boost pressure from the map sensor, or they have a stock fuel pump with no in line to back it up, and most stock pumps can't keep up with an fmu's demands.
04-30-2009, 10:46 AM
#9
0.5 BAR
Join Date: Mar 2009
Posts: 137
Anymore, there is a ton of technology out there, I'm sure you can find some good lesser expensive tuning route. I just don't like FMU's. They do the job... get her done dirty! If you are just wanting to get the job done dirty..... Run it baby!
