XTwinTurbo

Hoping you can provide some pointers before I give up on my supercharger. I've been struggling with a slow Vette for months and will yank out my blower if I can't get it moving.

I have the symptoms of a weird slipping belt at WOT. Starting at approx 3000 rpm the car just loses power and gives me that misfire/injector dropping feeling. Driving in part throttle not an issue only WOT.

I don't know if it's the belt as I just swapped out the belt musclling on a 1/2" tighter belt on. I can't even beat cavaliers in a race when this happens.

Done to the car:

- vortech v1 blower with smaller pulley for about 12 psi boost.
- issue happen with and without ati intercooler.
- running a 8 rib belt/pulley conversion.
- new injectors and tried different tunes.

Could I have clogged catalytic converters?
Could it be a weak tensioner and actual slipping?
Anything else I can test?

Thanks.

P.s. I have 93VettePilot's turbo kit sitting and thinking it's time to swap over but I sure will miss my AC.

Tom400CFI

It sounds a LOT like you're running out of fuel. Does it at WOT/high RPM...but not at lower throttle OR lower RPM? I'd have a fuel pressure gauge on it pronto.

As for clogged cat, it's possible...but I'd think you'd also see a corresponding "overboost" on your boost pressure gauge if that was the case. If the exhaust can't get out, it seems like things would back up and you'd end up w/higher manifold pressure.

drive it

[QUOTE=Tom400CFI;1588174893]It sounds a LOT like you're running out of fuel. Does it at WOT/high RPM...but not at lower throttle OR lower RPM? I'd have a fuel pressure gauge on it pronto.

Second that. Probably a lean misfire. What fuel pump are you using? You say different tunes-with a fmu? What size injectors?

XTwinTurbo

[QUOTE=drive it;1588176529]Running a walbro, high flow high pressure in tank pump. Also running a Kenne Bell boost a pump voltage controller. 42lb/hr SVO injectors with my own tune using LT1edit.

It does it a WOT low rpm as well as WOT high rpm.

Tom400CFI

Well...you need to start w/the basics, so again, I'd put a gauge on it to confirm that you you're getting adequate pressure at all times.

illenema

What type of blowoff valve is being used. Any power increase over stock? Picture of setup would help

XTwinTurbo

Thanks. Will have to try to get some readings and logs.

XTwinTurbo

You may be on to something here! Running a HKS SSBOV dumping into atmosphere. Truth is the car made a great psst sound between shifts that has now disappeared (no sound). Maybe it is leaking pressure at wot or worse floating open.

Thanks for the thought, going to test this next.

drive it

[QUOTE=XTwinTurbo;1588177191]Also what's the duty cycle hitting with your injectors?

XTwinTurbo

[QUOTE=drive it;1588180120]Will have to get a logging run done and share the info. When I last tuned it with a wideband, I kept duty cycle below 80%. Have to check this hasen't changed.

smooth1990

[QUOTE=XTwinTurbo;1588185649]Do you have a fuel pressure gauge in the car? That is the most important thing to have when tuning for boost! If you do, watch for it to fall off. Rule of thumb is 1 PSI per LB of boost.

Do you have a wideband in the car? What is your AFR at when this happens?

Lastly- do you have a boost gauge? is your boost falling off? that is a sure sign of either a inlet restriction or a slipping belt.

You mentioned an 8 rib setup. Im guessing this is a blowerworks kit. If so I highly doubt you would be getting belt slip that bad. A tell tale sign would be black belt dust around the upper and/or lower pulley. I assume its a dedicated 8 rib belt?

I had a similar problem. The car felt like it hit a rev limiter up high. Actually I had those same symptoms with a few separate issues. The first was ignition. If you have a LT1 car, the optispark wont pull much over 5500 rpm with 10 psi or more of boost. I fixed that with a CDI box. The second was the intake elbow going to the air filter was collapsing under boost and restricting all flow to the blower.

If I was in your shoes I would get some gauges if you dont already have them. It sure makes diagnosing these problems alot easier. between the AFR, boost and fuel you can locate the issues you come across quickly and fix them.

Good luck !

smooth1990

Also another thing I would be concerned with is the single walbro pump. Even with the boost pump I dont think it will provide enough fuel for 12 lbs of boost.

Lets start at the beginning. What are all the mods on the car? what year vette?heads? intake? cam? injector size? exc.

XTwinTurbo

Thanks all for the input. Today I pulled the BOV and plugged the hose. This woke up the car and it started running like a scorched ape, spinning tires like it use to. Looks like I have a failed BOV and will need to replace it.

Appreciate the thought illenema and thanks to everyone as I will data log and get the car tuned in since it's been a couple years.

illenema

!!!

FrankieD

Great job illenema for nailing it.

Scootin_Z

[QUOTE=smooth1990;1588192479]what did you do to fix your intake collapsing? I'm having a similar situation where I get plenty of boost and all the sudden it falls off and I know that boot is collapsing a bit, but I'm not sure I have the same setup as you as the first thing is my air filter then pipe. I'm also wondering if my filter is too small because there's not a lot of room down in the front well. Do you have any photos of your setup?
Thanks

BlowerWorks

Number 1 on ANY vehicle is fuel pressure and even more so on altered high HP engines. So to fulfill Number 1 you need an in-cockpit ELECTRONIC FP gage like Autometer etc. Forget the mechanical style and their 'stuopido' isolator !!!!!!!! LOL

Fuel pressure first and then we can move on with the diagnosis !!!!!!!!!

greg

Scootin_Z

Got one, so what should my ideal reading be for 7-8 pounds?

gmjr

fuel pressure gauge a must on turbo or supercharged engines whether driving on the street or at the strip you always want to know what the fuel pump is doing GMJR 1989 d1 procharged vette 10sec. street car.

Best210

I am having a similar problem with my car. Did you leave the BOV in place and just plug the vacuum hose to test your BOV?