Charge temps are INORDINATELY high with the supercharger, as high as 250 F, as logged on the racetrack! They're even very, very high with the intercooler we are running. The car will lightly det on anything but 110 leaded even with a conservative tune. It NEEDS the fuel to stay cool. Our motor has low static, but relatively high dynamic compression, unlike, say a Honda motor.

BSFC numbers are different for different engines and different FI systems. Also revolutions will change duty cycles as well. We've run as high as 7,500 rpm, hence the need for even more fuel.

For a street supercharged car, you could "probably" get away with 550s, but you're cutting it so close, not in theory, in real on the dyno, and on the track testing, that going with 700s will be the safer bet.

 

Thanks for the great info Dan, and everyone else. I like to know the workings of things before I make a choice. I have decided to pic up the 700's. I'll let everyone know how it goes as I get things together.

 

With the aem fi/c you can change the injector pulse to help with idling

 

idle isn't bad for me. it stays steady around 800 rpm when the car is warmed up.

 

Excellent, the idle was one of my main worries. It kooks like all of my questions have been answered and I can go ahead with my decision to purchase the 700cc injectors. Thanks again to all the people who responded both the known and not so know people. Always good to get opinion from many people.

Again Dezod I didn't want to make it seem as if your guys weren't right or didn't know what you were doing, but my main goal was to get the facts behind why 700cc is necessary, I like to know what I'm getting myself into.

 

Good real world comments from Dan, but with all due respect...not exactly the fulle story.

Can't really compare the challenge of INORDINATELY high temps in your race car.

1 - DG's car is overboosting his pulley. With the AEM setup he is rev'ing past the stock limiter, that means more psi, and more power, and more HEAT than would be spec'd on the NST pulley he is running.

2 - Running an A2W intercooler on his setup is LESS efficient than an A2A...and during his races I would not be surprised to see higher temps that just don't go away. For Time Attack style racing, his is actually not the ideal setup.

So why is that? Let's cover a little thermodynamics. See, the benefit of water over air is it's ability to absorb energy and heat faster than air. Not only that, but the reduction can be made to be LESS than ambient temperature. Can't do that with A2A, right? How is that possible with A2W? An Ice bag, gets your liquid colder than the outside air...Guys on the drag strip routinely do this. Of course ice melts, but remember that, I will come back to it.

So now if A2W is sooo good (smaller core's too, right), then what's the downside? Well, for 1 you need a heat exchanger to take that heated water (we picked up from the hot air in our cooler) and lower it's temperature down. So to cool that water you have a big radiator and it reduces the temp of the water passing through. Under normal driving, that is lowered again by air passing over the radiator fins. You'll never get to ambient, so it lowers it a bit. Then it travels along its path to the intercooler and exchanges heat with the air (lowering it). but guess what? We've made the water a little warmer than before. The viscous cycle continues. The relative temp of the water keeps getting warmer and warmer since the air in the radiator can't cool it fast enough. As it gets warmer, its ability to cool intake charge air is hampered. It cannot really cool (the water) until you come off throttle. Dan does not do this.

So the harder and longer you drive your engine, you actually have diminishing returns on an A2W setup. That and the bit of extra weight (and complexity) gives people pause. And this is the reason why MANY use it for drag events, where the car is going all out for less than 30 seconds...especially with Ice as mentioned.

In Dan's situation, he has his car on full tilt for hours on end. Of course his temps will be high and stay there. Depending upon how hard your drive your DD, the same may be true for you.

So I'll repeat what I said to the OP earlier. Measure, measure, measure. The intertubes is good for general info and anecdotal info, but each setup is different. You can measure your duty cycles, air temps and pressure drop with the right equipment. Don't even believe me, do the math on your own.

And if you want REAL world info, the reality is that in real world driving, I barely get into boost. If I accelerate like a normal citizen (not even a granny), I can get up to and maintain 70mph with out even going into boost. If I push it, maybe 2psi along the way, then zero at cruising. You need to be going full tilt to hit your max boost. So my advice would be to size your solution to your application.

 

Point taken.... granted I Boost like a mad man!!! Definitely put less stress on it than at the track, but I do drive way harder than the average Joe. I boost whenever space and environment allows.

P.S. I will be running a 1.2 gallon reservoir to help to give the system little extra water to absorb any excess heat.

 

So that we're explicitly clear, we ran lean and watched both AFRs and IDCs on the DYNO, before any track data was collected a year ago. That's when we decided to use 700s. Truth is that 600s would have been perfect back then, but there aren't DROP-IN 600s. Dezod has good 700s and that gave us plenty of headroom on the IDC side.

And as far as additional revs, we've yet to see anything higher than 11 psi on the dyno or the track. The original poster asked for a setup with 11.5 psi.

 

Hey Dan! Thanks for chiming in on this thread with a multitude of facts to provide to this community. As always, you're input is much appreciated.

 

Yes, Dan very good, I like. lol

 

watching.

 

watching.

 

550's are what the 12lb s/c people are running. I was running the stock injectors when i had my 10.5lb pulley on and they were as high as you wanted to go w/ the stock s/c injectors

 

very informative thanx 4 the right ups

 

How big can the injectors be before you need to upgrade your fuel pump?

 

I think you can run 700's with the stock pump, even more if you get a return setup.