Went and dynoed my car today hoping for somewhere around 270rwhp and 400+ft/lbs

put my car on the dynojet, and did a 2nd gear pull 3000-5000rpm.

at idle, the car was at about 14:1 A/F, but at 3k it would be down to 12, and by the time it was hitting 4k, it was at 11 and would drop down to 10 by the time it hit 5k.

also, the car only put down 215hp and 310ft/lbs.... a lot less than i had expected.


motor:
383ci, 64cc swirl port heads, stock tpi, hooker long tubes, h-pipe (dynoed straight exhaust), new msd 8.5mm superconductors, msd blaster 2 coil, accel shorty header plugs, new ignition module, new cap/rotor, 255lph fuel pump, and the car has an adjustable fuel pressure regulator on it.

the pressure was set to @ 50psi for the dyno pulls





my question is why does my A/F ratio get so horrible throughout the rpms?

i know that the egr valve is causing the ses light to come on when cruising highway speeds, but i dont think that would cause the car to run so rich at WOT... and why does it only have 215rwhp and 310ft/lbs??? i see everyone elses tpi putting down 350+ft/lbs at least, and thats with a 350

(all sensors have been checked with a MODIS and verified in normal operating voltages)

 

You should be using 3rd gear with and auto and 4th gear with a stick when you are on the dyno. Since you used 2nd gear you will see a 5 to 10 HP increase in your numbers with the gear change. My guess on the A/f ratio is that you need a chip burned to compliment your changes. You have a SD computer system and the computer does not know what is going on in your engine and it is addin in too much fuel. The swirl port heads are probably restricting the air flow and the computer is adding in too much fuel.

 

I am thinking that your heads are a serious bottle neck. Not to sure about the rich issue, would need more info? Have you tuned it at all? What injectors?? Also depends on the dyno as far as HP/TQ #'s, they can really vary! Does the car feel strong?

 

This was done on a dynojet, and i did it in 2nd gear because i have 2.73 rearend gears and a 105mph speed limiter (305 computer) because the car came from the factory with crap tires, so i wouldnt be able to go all the way through 3rd gear before hitting the limiter.


the camshaft in the motor is 212/218 .444/.454 110lsa, and im not sure about the fuel injectors... the guy i got the car from said he had 40lb injectors on there but i dont see why he would have put that huge of an injector onto the motor.

and the car does feel strong, just not over 4500rpm. the motor makes a lot of low end torque, but i wasnt able to dyno it below 3k

 

Oh ok, so you have a cam also. The heads and intake are going to murder your top end, that is a fact for sure! As far as the other issues, you are really gonna have to have that car tuned, sounds to me like nobody ever touched that prom if you still have the speed limiter. Once you have the car tuned properly, then you will be able to get a better idea of what the limit of that combo will be. I already said it, but heads and an intake will really wake the car up, a 383 needs to breath!!

 

the cam/head/intake combo was made for lowend/midrange power... hence the 212/218 duration.

im debating swapping the tpi for a carb'ed setup

 

TPI and swirlports? I'm surprised you got that much out or it.

 

The heads and lack of tune are what is hurting your performance. A carb intake will still not give you a big increase in power because the swirl port heads are restricting the airflow into the engine.

 

yeah man, why would you do that lol, it seems to me that your motor is totally mismatched???

 

TPI gives up around 4800 rpms.

With siamesed runners, you could stretch that a bit further, but 383s need more than a TPI can provide.

Do an LT1 intake swap, Stealth ram swap...something! Don't give up on FI, and go carb'd. You'll lose street legality here in Austin, unless you have a friend that will look the other way. Not only because of the carb, but sniffer test too. Road side sniffer tests are coming to Austin. They've already been spotted in pre-tests here.

 

i didnt put the motor together myself, i bought the car with the motor/heads/cam already put together, i just did a ignition tune up and new fuel pump, otherwise i havent touched one piece of the drivetrain.

 

Youd be suprised what you can pick up with a tune. For a 383, a cheap upgrade would be to install completely hogged out SLP runners with a hogged out plenum to give you more upper end and less torque.

 

The 383 TPI in my `88 Iroc ,700r4, is California smog legal and probably the fastest car I have driven in the street. This includes my `69 Roadrunner and `71 Charger. It also has stock exhaust.

 

your way down on power. my dead stock 350 TPI laid down 190/305 in third gear.
with a stock unported TPI, falling off at 4500 isn't too bad.
those heads are killing you. another thing is the 305 chip. you need at least a chip for a 350.
i also wonder if they put the right knock sensor in.
40 on the injectors is big, but he probably had to do that because of the 305 chip.
my suggestion is to learn how to burn your own chips. you'll never find any after market chip that will work right.
the computer won't like that 110LSA cam at idle too much, but there are ways around it with doing your own chips.
a good set of heads & doing your own chips will go a long ways toward good performance out of it.
one of the nice things about FI, with a properly tuned chip, you can get decent fuel mileage on the highway, some of the guys in DIY-PROM with some serious motors are knocking down better than 25 MPG highway, some 30+, you can't do that with a carb.

 

You are getting way too much fuel. 40 lb injectors... why in the world would you have the fuel pressure set to 50 psi when using 40 lb. injectors and a 305 PROM that (if it's a stock PROM) has an injector constant of 19 or 20 lbs. The computer is doing it's best to compensate, but forget about ever being right with this setup.

For starters, you should set the fuel pressure back to a stock 44 psi.