Re: [DML] Supercharger help

[William T Wilson <fluffy@xxxx>]

On Sun, 18 Jan 2004, mcookwwi wrote:

> A few questions I have that may save me some time and mistakes:

I agree with Bruce - these are complex questions!

> 1) What is a safe boost level (psi) to use with this setup on a stock 
> delo engine? I am thinking about getting a 10 psi pulley and using an 
> adjustable pop-off valve to limit the max boost to whatever I set. Is 

Any boost level is safe if you are set up for it. If you are planning on 
retaining the stock fuel system and not using an intercooler, you should 
be safe with about 6 PSI. By modifying the existing system to increase 
fuel pressure you can get a more or less reasonable state of fuel delivery 
to match a supercharger.

The DeLorean PRV is (by modern standards) quite low compression. Even in
the early 90's there were cars stock with 9.0:1 and higher compression
ratios, significantly higher than the DeLorean, running factory-stock
setups with 8 PSI of boost or more. The difference is that these cars
have modern engine control electronics. With the necessary fuel and
ignition system modifications you could probably run about as much boost
as you want to without any internal engine modifications. This may be
more than you want to get into - but I bet you could get 250+ HP out of
the stock engine.

Since you are using a Vortech supercharger it is almost like a belt-driven
turbo. You probably will have more in common with a turbo install than
with something like a Roots supercharger.

> this possible? Where can I get a pop-off valve? (I'm not talking 
> about a blow-off valve)

I'd recommend just getting appropriate sized pulleys and not worrying
about any more complex plumbing.

> 2) What timing should I use?

Less than stock? Beyond that this will depend on your power targets, how 
much boost you run and how you modify the fuel/ignition system.

> 3) I assume high-octane rating fuel and possibly H2O/methanol 
> injection may not be a bad idea?

Use the highest octane fuel you can get, especially while you are just
getting the new system dialed in. Most major cities have somewhere you
can get 100 octane unleaded racing gas. It's good insurance on an untuned
setup, but you should be able to get by with regular premium once it's set
up.

Methanol injection I would not worry about, you are not building a P-51 
here :) Water injection is actually a really cheap and easy substitute 
for intercooling, but it's sort of a big hassle because you need to always 
keep the water injection tank full and the pump working, etc. I think of 
water injection as something that drag racers use, not something for a 
street application. But you could, it's just a matter of hassle.

> 4) Should I use an aftercooler? (where should I put it and where can 
> I purchase one that will fit?)

If you plan to run more than 6 PSI of boost, you should use one. Finding 
one and making it fit, well, that's the fun part. I'd recommend coming up 
with some sort of air scoop (route air in from the nonfunctional side 
scoops? A snorkel sticking up above the car? A water intercooler plumbed 
into the engine cooling system? All sorts of ways you COULD do it...) As 
far as what to use, just go to the junkyard and look at the turbo cars 
they've got. It's just sheet metal, you can put it practically anywhere, 
and the intercooler does not care if it is hooked up to a turbo or a 
supercharger.

> 6) What system can I piggy-back to the existing system to control all of
> this or should I just replace the existing ignition and fuel system?

There's no piggy-back setup for the DeLorean.

If you want big power gains, replacement is the way to do it. If you are
happy with 6 PSI of boost and ~175 HP, you don't need to. Just consult
someone who's put in an Island turbo system and make the same fuel
modifications (essentially, this boosts fuel pressure causing more fuel to
be injected based on the same signals to the injectors). An inexact, but
surprisingly effective, approach.

For big power, switch to a draw-through carburetor setup or (better) to an
aftermarket EFI like a Haltech.