**Yes, I made this exact same thread on DSMtuners, but I did so because I know not everyone here uses that board, and vice versa. I know there's a lot of knowledge on both forums so I'm trying to maximize my chances of getting helpful input.



Ok guys, first of all thank you in advance for any help you may be able to give. Some of you may know I turbo'd my car about a month ago. Well I finally hit the dyno this weekend and got a rude awakening. I will list the key parts of my turbo and fuel setup below, as well as post my graphs. Then my questions at the end.

Engine:
Howell stroker motor including JE/Eagle combo in the bottom end, P&P head with the Crane cams and so on up top, you all know what it's got. And if not, just look at my profile (link is in my sig), I've got most of it listed there I think.

Turbo:
Turbonetics T3/T04e 50-trim. It's a custom setup based on a Star kit platform. I'm running 8psi via my TiAL wastegate's spring pressure only, no boost controller. NGK BKR7e plugs gapped to .028 if that is important to know as well...

Fuel:
Stock injectors, new Walbro 255lph high-pressure fuel pump, used Vortech 12:1 FMU, and a Synapse missing link also used.

In case it matters, I run the vacuum line to the FMU from a vacuum distributor block. The block gets its vacuum source from the brake booster port on the IM, and distributes to 4 lines - my boost gauge pressure sensor, my bov, my FMU, and my brake booster.

The graphs are self explanatory. First is horsepower, second is torque, and third is my air fuel ratio. All three pulls were in 3rd gear. Blue is my first run with my usual setup according to everything I described above. Red was my second run, which I stopped short on because my AFR jumped just the same as it did on my first run and didn't want to risk it. The only change I made for that run was swapping the FMU vacuum line to the port on the throttle body where some vacuum source comes from in case it had a stronger vacuum signal, perhaps making the FMU give me more fuel (didn't help, actually got worse). And lastly, the Green was my third run. This time I completely took off my charge pipe running to the throttle body. This was just a test run just to see what my AFR would do without any boost. I didn't do any more pulls for obvious reasons, I didn't want to blow up my motor or anything.







Alright, now that you have seen those awful graphs... yay I broke past 200 whp and wtq!! But in all seriousness, I'm definitely scared by that air/fuel jumping to 15:1 at peak torque. I learned a valuable lesson - when I got all my turbo parts, I was (and still am) on a tight budget and couldn't afford a wideband. I sure regret that decision because it would have been nice to know how dangerous the car was running these past 3 or 4 weeks. Granted, there is a slight chance the sniffer wasn't getting a good reading... but it was within a half a point of the wideband gauges on the other 2 turbo cars that dyno'd with me, so I'm afraid it was pretty accurate.

Now I guess I need to do my best to stay out of boost whenever I drive the car until I can solve this problem. It's my DD so I can't just let it sit, I do need it every few days.

Questions:
Could this be an issue with the FMU not working properly? This is an extremely common fuel setup for us turbo 420a guys running 8psi or less, right? That's why I felt safe until after the dyno. I would expect we run 40-43 fuel pressure stock, then add 8psi x 12 (FMU rate), that's an additional 96 psi... can the Walbro support almost 140 psi of fuel pressure when at full boost? What's going on, how is this such a common fuel setup yet I'm so lean?

I have run smooth and strong, seemingly perfectly fine this whole month until Friday night. I never encountered a problem since I went turbo till that night. I was at the 1/8th mile track, and unfortunately I split my fuel return line between the fuel rail and FMU. I only got to make 1 run before I noticed the fuel pouring out below the car. I replaced the line immediately. I don't know if that has anything to do with the situation or not, but in case it might, I added it into my story here. I went to the dyno the next afternoon, Saturday.

Solution?:
So... what do you think I should do now? Remember I'm a college student with practically no money left to spare. I will be working in 2 months, hoping to grab the Plug & Play MSnS when it is released, but right now I'm almost broke.

Could the FMU be malfunctioning somehow? Is there any way to test it? Can I get larger injectors and an SAFC-II or something (don't know much about them yet) and run the same 12:1 FMU + Walbro setup and be safe then still at 8psi? What are my options while still on a strict budget to get to a safer fuel level?

Is there a chance I'm broken my motor and don't know it?

I apologize for the length of this thread, but I wanted to be clear, and leave no detail unmentioned. If you have any input, please post it. I need your all's help!

Thank you!

I'd grab some 310c/min injectors and an SFMU and go from there. 12:1 FMU's and big fuel pumps are workable, but they are far from the best solution.

Would the slightly larger injectors and an SFMU work by themselves just on a certain sfmu disc, or does that setup need to be controlled and tuned by an SAFC or something?

And any idea how this is happening? Many others seem to be fine with this setup.

Originally posted by chris712vt
Would the slightly larger injectors and an SFMU work by themselves just on a certain sfmu disc, or does that setup need to be controlled and tuned by an SAFC or something? And any idea how this is happening? Many others seem to be fine with this setup.

You may have a crap fuel pump. The reason you're seeing a lean spike at max torque could be that you're not able to get the fuel pressure up high enough to maintain a sane A/F until the pump catches up.

is it infact a waly and not a knock-off? they max at about 115psi so your 140psi is wishfull thinking. i have extra 315cc injectors i'll give you for next to nothing then you can get and sfmu and boost happy. btw, with good supporting mods the stock injectors will handle very little boost. pm me if you want the 315's

Yes it's a real walbro 255 hp, got it from extremepsi.

PM on it's way :), thanks!

And if I'm going to move up to this larger injector + sfmu fuel setup, two questions:

1 - Do I need anything else, such as an safc, or can it run just on the sfmu?

2 - Will this now allow me to run a little more boost while still at a safe afr? Like 12psi?

you don't need an afc but you will need a w/b to tune the rise rate. 315's are considered good for 9-10psi but w/o big suporting mods i ran 13psi. it all depends on hp.

You could run larger injectors just not to big with the fmu. Yes if you get larger injectors you will need a differant disc set up. Im running 24lb injectors for now till i get my sfmu and so forth and the only reason i got an safc now is cause i keep getting the rich code, so i wanted to lean it out a little. I have no probs with my set up and have been on it for about 2 months now. TRE 255 pump vortech 10-1 bosch perf 24lb injectors and running pig rich till 7ooo