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Old 07-30-2020, 01:18 PM   #1
Fastest FWD GA
MilzyZ34's Avatar
AKA: Mike
Join Date: Aug 2003
Location: Dayton, OH
Age: 40
Posts: 963
Vehicle: 1999 Grand Am GT
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Milzy Motorsports M90 Supercharger Kit

We've been working on a supercharger kit for the 3100 and 3400 cars for some time now, and over the last couple of weeks, we've pushed the prototype project through to completion. As you may or may not know, the kit is based off of the M90 supercharger found on the 3800 powered vehicles, with options for both the Gen III and Gen V M90 blowers. You can find details for the kit on our site, here ...

So, in order to test out the kit, what I decided to do was to take the prototype supercharger kit, with a shortened version of the Gen V M90, and install this on the stockest vehicle I could find. The vehicle I selected was my own 2000 Alero 3400, in rougher than average condition. It has about 200k miles on it, and was pretty rusted out. I bought it a few years ago with a charging system problem, but later found that the engine was pretty rough too, as it was leaking water/coolant out the exhaust any time you ran it. I wanted to test this with a completely stock engine, so last year I bought an engine from a junkyard for supercheap, with about 200k miles on it. When I went to install it, apparently it had been rained in, so the rings were rusted to the cylinder walls. A replacement was gonna take a few days that I didn't have, so I picked out an ok looking shortblock from my core pile, grabbed some heads, intakes, and valvetrain off the shelf and put together a complete stock motor. It's essentially a 2000-2002 3400, with unknown miles, probably around 150-200k, and sealed up with new gaskets. In preparation for the supercharger, I decided to install a few parts on the car to help it deal with the added boost. So I installed a 2.5" downpipe, 180 t-stat, AL 104 plugs gapped at .045", 60lb injectors (because they were part of the prototype guy's parts list), and 93 octane fuel. I opted not to install the Walbro 255 fuel pump as the car was very rusted out, and I was under the gun time-frame wise and didn't want to get stuck for a couple days making new fuel lines, or brake lines or anything else if I opened that can of worms. I also did not change the fuel filter for the same reasons, and decided to cross my fingers on both of these. After all, it's my car, so I can make that decision.

So Friday we went to the dyno, and did some before runs. A completely stock engine makes on average 135-145whp, so we weren't expecting much, but were pleasantly surprised with 170.8whp with the mods we did in preparation of the SC.

Then I installed the supercharger while the car was on the dyno, which took about 20 minutes or so to do, keep in mind I already had installed the fuel injectors a few days before, and had already worked out the belt layout and everything else.

Now the 3400 has a smaller crank pulley than the 3800 does, which means that it's going to take a more aggressive pulley drop to achieve the same blower rpm. The ratio of the two crank pulleys is roughly 6:7, so that's the ratio on pulley size versus SC rpm, although this does not factor in the flow differences between the 3400 and 3800. After we got the idle air fuel/fuel trims worked out, dropping pulley sizes, tweaking the timing advance, and making adjustments to the wide-open AFR, we ended up making 226.3whp and about 246wtq, which equates to roughly 283hp and 308ft-lbs at the crank. This was achieved with a 3.0" pulley which had a somewhat gradual boost curve starting out around 8.5 psi down low, 10.6 psi at max hp, and spiking to even 11.7 at redline, coupled with 11 degrees of timing advance. While this is not an earth-shafttering amount of power, it is impressive none-the-less. A stock 3800 series III Supercharged L32 engine makes 260 crank hp and 280ft-lbs at the crank with the same blower, and 75mm throttle body, and although this is with the stock pulley pushing about 8-10 psi of boost, it also has 13+ degrees of timing advance, not to mention the displacement differences between the 3800 and 3400. As for the 3400, it has a more efficient cylinder head design, and higher compression, although valve sizes are a bit smaller. All and all though, I am very happy with the results, and I think what's pretty impressive is if you compare the numbers we got with the 3.0" pulley to a stock 3400, you're gaining about 108 crank hp from this supercharger and supporting mods, all of which can be installed on a stock 3400 car in about an hour and a half.

One more excuse for the books, it became apparent the last few runs as we were making fuel changes to richen the ratio at the tail end of the run that these changes were not taking affect, and we could see the inj pulse widths raising to compensate, which lead us to determine that the stock 200k fuel pump could not keep up with the amount of fuel we were demanding, and we had to let off the throttle at 5700 rpm instead of 6000. We're not sure if it would have been a higher dyno number with a better fuel pump. We were trying for a ratio of around 11.5:1, but at 5700 when we let out, actual ratio was 12.6:1

Dyno sheets below. I also have a couple videos on the dyno and also driving it on the street after the dyno. I'll have to see if I can attach these as well.
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Name:	MMS SC Alero 226.3whp.jpg
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1999 Z34 - Was a Stage 3 3800 Supercharged, but not fast enough so I have some new plans for her.
1999 Grand Am GT Race Car - 12.1 sec ET, STOCK motor, 10 psi
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