VEC2 tuning issues. Not getting fuel???

[g3t_t0rk]

Hey all. Today after 5 hours of tuning, we called it quits because the car simply isn't getting fuel past 4000rpms. It made 3 successful pulls and it made 545whp/599wtq without water/**** injection but soon after, the car kept leaning out past 4000 rpms. We'll dump fuel in for 4k+ in the VEC2 but it doesn't seem like the car is getting fuel... Am I missing something here????

EDIT: Mods are Roe 2.4L Kenne Bell, 8 lb pulley, 255lph Walbro, and VEC2. Currently wired for water/**** injection as well but I'd like to zero in on the S/C tune before adding water/****.

 

[Red Snake]

Call Sean Roe.

 

[uvbnbit]

Fuel pump? boost a pump? fuel filter?
check the fuel pressure

 

[g3t_t0rk]

Fuel pump? boost a pump? fuel filter?
check the fuel pressure

The car has a 255lph Walbro if I recall correctly

 

[MoparMap]

Are the injectors maxing out by any chance?

 

[uvbnbit]

The car has a 255lph Walbro if I recall correctly

hook a fuel pressure gauge up (tape to windshield) and go for a ride, see if pressure is staying higher in the RPM range.

 

[Will at RSI]

If you are only running a single Walbro 255, I would say that you are most likely found the limit of you fuel setup. Typically a 255 is good to about 600rwhp, but would be less on a S/C car.

 

[Red Snake]

^ This. I am running the BAP in conjunction with the 255 on my set up.

 

[speedracervr4]

I would check your injector duty cycles and fuel pressure. I have a set of green top injectors if yours are maxed out (doubtful).

 

[g3t_t0rk]

If you are only running a single Walbro 255, I would say that you are most likely found the limit of you fuel setup. Typically a 255 is good to about 600rwhp, but would be less on a S/C car.

I think you're 100% correct. A friend just so happens to have a 340lph fuel pump. Would this be big enough?

I would check your injector duty cycles and fuel pressure. I have a set of green top injectors if yours are maxed out (doubtful).

Using the VEC2, we're only at 70 out of 200 so we're only at 35% duty cycle. I haven't looked into fuel pressure but more and more it seems to be the fuel pump.

 

[EllowViper]

What year car? The fuel basket and outlet design is different in the later cars...aka on a stock system my 01 GTS had no problem with the stock fuel pump @ 8 PSI. Lots of duty cycle left with green tops as well. By swapping out the stock line with -an6 and aftermarket cleanable filter, my stock PSI went from 55 to 65. The stock filter combined with the small diameter steel line is restrictive and IMO acts as an additional restriction that bleeds off fuel pressure in the basket-mounted regulator. Remove that restriction and the fuel injectors serve as the first restriction in the delivery system and pressure to the rails will see higher PSI as a result. As least my before and after fuel pressure readings indicate such. Or simply my fuel pressure regulator diaphram/spring in the basket convieniently got tighter on its own!!

 

[g3t_t0rk]

What is the fuel pressure supposed to be for a Gen 2 Roe S/C??

 

[speedracervr4]

55 psi....

 

[g3t_t0rk]

55 psi....

Thank you! I went with this fuel pump.

http://www.lethalperformance.com/03...sionx/divisionx-stryker-340lph-fuel-pump.html

 

[uvbnbit]

Did you check the fuel pressure or have you determined that's more than likely the culprit. Let us know how this one works out. Hope you get 'er fixed up!

 

[Jack B]

Be careful about another pump, when you use anything but a viper fuel pump the bottle does not get filled. You may overcome the fuel pressure/flow issue, however, you will suffer fuel starvation during launch and hard cornering if you have anything less than a 3/4- to full tank. I did a write up about six months ago, do a search.

The Gen 3 pump is a 255LPH animal, if the problem is fuel pressure/flow use the Gen 3 pump with a BAP and you will solve your issues, that combo is good for approx 800-850 hp on a NA car.

One item to look at - do you have the injector offset correct? That could cause an issue and it would be very obvious at WOT/high rpm. What size injectors do you have? The earlier posts were right about monitoring fuel pressure, you have to log that PID. If you want a fuel pressure sensor, I have one you can have for $25, bring the 0-5V into the vec, I haven't used the VEC for a while, but, I beleive you can bring in an external sensor signal.

I think you're 100% correct. A friend just so happens to have a 340lph fuel pump. Would this be big enough?



Using the VEC2, we're only at 70 out of 200 so we're only at 35% duty cycle. I haven't looked into fuel pressure but more and more it seems to be the fuel pump.

 

[Red Snake]

Be careful about another pump, when you use anything but a viper fuel pump the bottle does not get filled. You may overcome the fuel pressure/flow issue, however, you will suffer fuel starvation during launch and hard cornering if you have anything less than a 3/4- to full tank. I did a write up about six months ago, do a search.

The Gen 3 pump is a 255LPH animal, if the problem is fuel pressure/flow use the Gen 3 pump with a BAP and you will solve your issues, that combo is good for approx 800-850 hp on a NA car.

One item to look at - do you have the injector offset correct? That could cause an issue and it would be very obvious at WOT/high rpm. What size injectors do you have? The earlier posts were right about monitoring fuel pressure, you have to log that PID. If you want a fuel pressure sensor, I have one you can have for $25, bring the 0-5V into the vec, I haven't used the VEC for a while, but, I beleive you can bring in an external sensor signal.

I disagree with the bolded part Jack. I run an intank Walbro 255 and a boost-a-pump. I can drive my car hard with the fuel level down to at least 1/4 tank with no starvation issues. Your post makes it sound like i would have to keep my car full all the time and thats just not true. I am speaking for first hand knowledge using this setup for over 4 years with not one single issue.

I could see having an issue below 1/4 tank but i dont push it that low.

 

[99 R/T 10]

Will at RSI also sells a Walbro 400, which would be an excellent candidate to use as an upgrade, but I also agree teh fuel lines and fuel filter is probably bottle-necking at higher RPMs.

 

[Blainne]

If you are only running a single Walbro 255, I would say that you are most likely found the limit of you fuel setup. Typically a 255 is good to about 600rwhp, but would be less on a S/C car.

Can't tune out a maxed out fuel system. IF the parts Injectors and pump are rated beyond what your pushing then it could be a defective part somewhere in the fuel system.