Cars making no HP, idk what to do.

[sharkbait11]

Ok So I just got back from a tune and came out with 227rwhp.

I have a powerdyne supercharger 6psi, ProM Mass air, 30# injectors, 78mm T/B, Magnaflow Exhaust, 255LPH Fuel pump, MSD ignition, FRPP 9mm wires, Bosch plugs.


The tuner said that Im making 10psi of backpressue from my midpipe and thats sucking up some hp. But i dont think it sucking up enough to make my car only 20hp and 8 tq more then stock.

 

[tag4car]

Need more info, What year?

 

[wmburns]

History? Did it produce more power before and less now?

Results of a compression test and leak down test?

 

[ChillPhatCat]

What engine do you have that made 207 RWHp stock? I'm guessing it's an early 4.6 in which case I'd expect it was making 180ish at the wheels stock... which means you're up almost 50 Hp. Did you actually have it dyno'd when it was stock? But yeah, we do need to know what year engine you have to really get an idea of what's going on. However, even for a non-PI engine that does seem a little low for 6 psi.

 

[2002BLGT]

we need more info ? is there black dust all over the front timing cover , could be the belt slipping on the blower

 

[mustang51js]

you might need a new tuner also,the only thing i see that can hold you back is the injectors, but i would think you should have no problem breaking 300rwhp with that setup

 

[sharkbait11]

Its a nPi 4.6. Everything internal is stock. I was deffinitaly expecting to see somewere around 300. Id be happy with 280.

The car put down 5 psi on the dyno. Like tuner put the gauge in and it hit 5. He also had a gauge measuring the exhaust backflow. But i dont think a midpipe would suck up that much HP.

 

[bhuff30]

If he was measuring backpressure and it got to 10psi, then you obviously found your problem. The back pressure should never ever exceed boost pressure on a supercharged car. That would be significant back pressure, even for a turbo car running 5psi. An efficient turbo would be around 1psi back pressure for each psi of boost. I only mention turbo engines because they SHOULD create backpressure because the impeller is driven by the exhaust gases.

Do you have cats or not? It is very possible you have clogged cats. If you are still running the stock H pipe, then you could see some very significant gains by switching it out. The stocker on my 97 had 6 cats. I gained .25s in the quarter by going to an offroad H.

Sounds like you need to listen to your tuner. If he measured backpressure at 10psi, then something is seriously not right.

Its a nPi 4.6. Everything internal is stock. I was deffinitaly expecting to see somewere around 300. Id be happy with 280.

The car put down 5 psi on the dyno. Like tuner put the gauge in and it hit 5. He also had a gauge measuring the exhaust backflow. But i dont think a midpipe would suck up that much HP.

 

[sharkbait11]

I trust my tuner. I am swapping that out first thing next year (trying to go month without buying car parts). I just dont think thats all of my problems.

 

[stangGT97]

I see you're also running Bosch plugs... they aren't the 4 prong platinum plugs are they? I don't think that would be helping your cause. You may want to try some Motorcraft AGSF-22Cs (copper, 1 heat range colder than stock) and see if that helps.

 

[sharkbait11]

The plugs are the Bosch Platnium Plus or whatever. Nothing to special. I think my tuner said to go 2 colder then stock.

If I do that what will it do? Like how will that change how my motor preforms?

 

[tfalk]

By nPI, I'm assuming you mean it's a 96-98 motor? Injectors are not your problem since your A/F is 11... that's a bit on the rich side even for a blown car and you are probably leaving 20-30 HP on the table because of the mixture. Is your MAF calibrated for 30 pound injectors? Did he look to see if the MAF is pegging? My Saleen was doing something similar since the MAF got pegged and the EEC didn't know what to do at that point.

There is clearly something going on around 3750 RPM since the graphs start falling off... Typically, a centrifigal should be making more HP at higher RPM than at lower RPM. That graph looks more like a roots blower, not a centrifigal...

 

[sharkbait11]

Mass air is fine. Its a ProM mass air. Its only running 3.9v at full throttle.

I went for the richer tune because shes a daily driver and i cant have the slightest risk of blowing it up.

 

[oxfordgt]

Well for one you have belt slip starting at 4200rpms but that is not causing your power loss bad enough. Those plugs are garbage change them. If your tuner told you to go 2 steps colder on your plugs with your set up then find a new tuner. Your biggest problem is your using a garbage powerdyne. It takes almost twice the hp to turn that thing compared to a vortech. Plus they are the most inefficient supercharger on the market. They are belt driven and not oil cooled. That is why you never see that blower being used.

 

[SVT32VDOHC]

TQ seems low too. I had a stock 4.6L with a mid pipe and catback and made 241RWHP and 284RWTQ...no tune either.

I'd get a second tuner to look at it.