WhiteWindsor

I know nothing about FI, so i thought i'd ask you guys. A guy has a nice coupe he's wanting to trade with a 306. It's got eddy heads,f-cam,1.72 rockers and intake. He has a v1 A trim charger will 11 lbs of boost. I think the a trim is the old style. He's putting 320 to the wheels now. Around how much would the charger add and what are your guys opinion on this piece? What supporting mods would i need to look for?

Thanks

nitrous_bob

11 pounds should make about another 150 , so it's no joke

if he had a build sheet or reciepts he would attest to that'd be nice, but anything your looking for it to have is all internal. not so much induction or fuel

but it should be in the neighborhood of 36 lb injectors, 255 pump, 70-75mm tb and 76+ maf

i would guess it to be a 10.80-10.90 car and make about 475-ish on the conservative guess, some of that et depends exactly how light he got it, and notches can be pretty dammm skinny if they wanna be

FoxGT

That's a pretty bad choice for what you're wanting. The A trim's compressor is most efficient around 5psi. It's very inefficient at 11psi. Here you can look at a map I have on it. To give you an idea, the pressure ratio you're wanting is around 1.75. Ideally you want to be as close as you can get to the blue island for max efficiency.

I'm not saying it wont work, I'm just saying don't expect big gains from it. It will still offer you a power gain. I would recommend trying to keep it below 40,000rpm. I believe 45,000 rpm is max.

1991LX5.0

The a trim will work fine, sure it wont be the most efficient at 11psi butyou can get a complete Atrim kit for under a grand. Forsome reason everyone thinks a trims arent any good past 350whp. Im making 450rwhp with an A trim at only 8-9lbs

FoxGT

I guess a better way for me to put this so it could be understood would be... If you're getting it for free, I would go ahead & put it on, but I wouldn't run 11psi just because I would want it to last. If you have to pay for it, get a different one. You will get a decent power gain as stated above, you would get a bigger power gain with one sized properly.

I guess another good area that I should mention as to what I was referring to by that, the speed required to get 11psi. You'll be at around 43,000rpm. at 8-9psi you'll be at around 35,000rpm. I'm about 90% sure vortech rated their newer models at 45,000rpm max impeller speed.
Yet again, I'm not saying you're going to damage it. There are plenty of people that overspin their superchargers. I have a friend that's spinning his at around 60,000rpm on one that's rated at a max of 55,000 & he has been doing so for about a year & a half now.

I'm not trying to say don't put it on, as I said; if it came with the car, I would for sure put it on. I'm just trying to give you information about it.

As far as the efficiency, the reason I said it was a bad choice is because when you consider where it is on the map & consider that centrifugal superchargers are known for being more efficient than the others at high end. When you put a 3 lobe roots sized right up against this it's going to be more efficient on high end than the centrifugal, which is saying something... I'm not sure if that's giving an idea of the point i'm trying to get across or not.