97 GTP

[xxxtreme36]

What will water injection do for me and where would be the best place to install this? Is it diff to install?

[Richard L]

Could you give me a few more bits of information about your GTP. I am not familiar with your car.

[xxxtreme36]

it is a pontiac gran prix gtp, this has the 231cu 3800 series 2 supercharged motor in it. As of now i have a full cat back exhaust with no u bend and no cat. cold air induction, custom dhp pcm, smaller 3.25 supercharger pulley, msd coils, ngk tr-55 plugs gapped at .045 for my 75 dry shot of nitrous, throttle body spacer with nitrous plumbed into it. Car runs about 12.90 in the 1/4 on street tires. have boost, trans temp, air/fuel, and nitrous guages. Is that what you needed to know?

[hotrod]

The only thing you missed was how much boost that pulley will give you, and if the supercharger is intercooled in any way.

As a generic statement, your configuration should benefit from WI, especially if your local pump premium gasoline is not quite up to the task for the boost your running.

Your plug gap strikes me as being a bit wide unless the GTP comes with a very good high output ignition, many cars running superchargers or turbocharges need to run narrower gaps than that to get reliable ignition. There is however a very good case to run the widest gap your ignition system will reliably fire the mixture at high rpm. WI might force you to close that down a bit.

The install of WI is generally pretty straight forward. It is mostly a plumbing job. You need to find a location on your intake system where you can place the nozzles ahead of the throttle body ( unless you want to mess with direct port injection ) It is in many ways similar to a nitrous setup.

On positive displacement superchargers you can gain more air flow by injecting ahead of the supercharger to pre-cool the intake charge before it goes through the supercharger. If you inject post supercharger you maximum air flow is limited by the superchargers rpm ( overdrive ratio) and the CFM / rev of the supercharger. No matter how much you cool the charge after the supercharger you will only get that max flow determined by the fact the supercharger is a positive displacement pump.

If you cool the air charge ahead of the supercharger you can make the supercharger act like it is a slightly larger CFM/rev design and actually increase your max air flow without changing the pulley.

If you are not intercooled WI will definitely help your setup as it will significantly increase the engines VE due to the cooling of the manifold air charge before it passes the intake valves. This not only will reduce your chance of detonation but will improve the engines ability to breath as the intake air charge will be cooler and denser.


Give us a bit more info on your boost, intercooling and what issues you have with fuel octane/detonation and perhaps we can help point you at some other considerations for you to look at.

Take a look around the site there are lots of useful info from other installs that should give you some ideas.

Larry

[Lysander]

xxx, just for your info I've been playing with WI for a very short time, and I thought I would share my experience with you.

I recently got my Aquamist kit running on my 1997 Grand Prix GTP. My mods are as follows:

3.8L pushrod V6 fed by the stock Eaton M90 supercharger, no intercooler
9 and 12 psi pullies
Headers
3" downpipe w/ stock catalytic converter
Borla cat-back exhaust
Cold air intake
Autolite 104 plugs gapped at .055 (one heat range colder than stock)
1.9 ratio rocker arms

Anyway I dropped from the 9psi to the 12psi pully yesterday and did three runs, I'm reasonably happy with the results. Does the car feel significantly faster? Not yet, not over race gas and the 3.25 anyway. One nice thing about it is that my car feels like it's a cool 45 degrees all the time, even when it's warm out.

At the moment I'm running some crappy washer fluid. I plan to do a couple of tunes with distilled water and various blends of methanol and distilled water to see what works best with my car. It also appears that my car is running fairly rich up top (again, this could be the washer fluid) but I don't like leaning for power without a wideband O2 setup. Once the install is all nice and pretty I'll take it to the dyno up the street and do a half dozen pulls. I have not played with different jets, pressures, or turn on points yet either.

Anyway, the facts are that before I had WI running I could run

9psi and +4-5 percent fuel up top

With WI I can run 13psi and no extra fuel to kill KR, but the car still does not feel any faster. I guess my trap speeds will tell the story the next time I hit the drag strip.

[Richard L]

Can you alter ignition timing?

I tuned a car a few month ago, 2-3 degrees made a huge difference.
If you start tuning for power with WI, you do have any possibility of switch map?

Or can the engine automatically advance timing in the adsence of knock?

[Lysander]

I have a 'canned' tune that advances timing ~ 3 degrees over stock in some tables (total of 18 degrees) at WOT. In ideal circumstances (the absence of knocking or pinging which would reduce ignition timing) I cannot increase my timing easily without purchasing some additional tuning equipment. What I can do is skew the fueling at various MAF sensor readings via a MAF translator. I can also increase boost to approximately 15psi with a smaller pulley I have on order.

[Richard L]

Originally Posted by Lysander

I have a 'canned' tune that advances timing ~ 3 degrees over stock in some tables (total of 18 degrees) at WOT. In ideal circumstances (the absence of knocking or pinging which would reduce ignition timing) I cannot increase my timing easily without purchasing some additional tuning equipment. What I can do is skew the fueling at various MAF sensor readings via a MAF translator. I can also increase boost to approximately 15psi with a smaller pulley I have on order.

What is 'canned' tune?

[hotrod]

I think he means its a predetermined tune, probably an off the shelf performance chip I would guess.

Larry

[Lysander]

Bingo. Dynotuned on someone else's car then sold as a recommended tune for cars with similar mods. It's not as powerful as a full on dyno tuning session, but no where near as expensive either