PxTx

I've been bouncing around the Audi boards and have found the most inspiration posted here, although the traffic is kinda slow.

I've got an old 4000 that I plan on having 2Bennett perform a 4.2 conversion on. In an effort to better understand the components I should select I am looking to hear more about the differences in the 4.2 engines. Specifically pros and cons between the 32 valve engines and the 40 valves.

Additionally I am looking to find out which motor has the lowest compression ratio. This is somewhat important because I am trying to supercharge the engine.

I've seen the MTM (sp?) unit over on the S4 forums which is a rather stealthy roots style blower and I really like it. I've also read here that Abt make a blower for the 4.2. I prefer the pressure curve of a roots blower, rather than a centrifugal so I'm not as interested in those. I also plan on keeping the boost under 10 psi so elaborate intercoolers are not nessisary.

Please don't tell me this car is a waste of money. The wayt I see it, the STI, Lancer EVO, and such are running rampant. Teh Infinity GTR will be here soon and this sleaper project of mine needs to get started. Any thoughts or input is welcome.

PaulW

It doesn't matter what pressure you charge you engine to, an intercooler provides additional efficiency to the charge. The higher the pressure your charge is, the more work must be done on the air, more engergy is added.....hotter charge.

An intercooler will increase the efficiency of the system. And wait until you put a 4.2 under the hood of your 4K, you'll be able to watch the paint flake!

Don't know what type of fuel injection system you'll be using or if you want to use the ECU that drives the ABZ (32 valve) motor.....but if you are going to use it, get the 32 valve motor because it does not use CAN bus signals except with the tranny.

The 40 valve motor uses CAN bus signals.....so using a stock ECU with it could prove to be difficult.

If using aftermarket fuel injection and ignition system, it probably doesn't matter which motor you use.

Good luck and post some pics!

PxTx

I am not against running an intercooler, I just want to stay away from elaborate plumbing and a big core. I feel if I can keep the boost below @ 10 psi or less, a simple water to air blow through between the compresor and the intake of the roots blower will work.

I know intercoolers increase eficiency, but they also require more presssue as they are a restriction and thus create a pressure drop. Yes, I've seen AWE's modified intercoolers witht he radious enteries into the cores, but I'm not talking lots of boost.

Spoke with Ken today and he says we'll be going with a 1999 or so vintage motor with a stock PCM. We'll stay away from 40 valve motors.

The budget is looking to be ready in May or so of '05. Pics are not very exciting right now as the car is stock with 104K on it. It will appear stock as best I can keep it for the spleeper appeal. The brakes and Koni's are first and I will get a set of BBS RX's for the period correct look- just cant decide if I go with 16" or up it to 17 even thought they were not a popular size in 1987.

Anyone else want to provide blower info? The 2Bennett kit is only for the S4's 4.2 so we have not nailed this down yet.

Kimchee

unless you are running a high boost pulley. =))

PaulW

300 HP in a 4KSQ is a lot of power....and it has 295 lb-ft of torque.....how much are looking to get?

BTW, it's a 10.7:1 compression ratio, so you will probably have to decrease compression ratio to charge it.....

PxTx

300 hp in a 4000 will not out accelerate a Subaru STI or the yet to arrive (late 2006) Infinity GT-R. Ken from 2Bennett say a 4.2 in a 4000 with their exhaust and software mods will be about 340 hp and go 0-60 in about 4.8 in my 87 with a rev limited top end of only 130 mph. If the top end is going to be that short, I want the car to 0-60 in 4.0 sec and run a 12.0 1/4 mile.

The fun for me at throwing money at an old car is the surprize effect when modern "hot" cars are unable to keep up. The biggest thrill is when people are unsuspecting of the ol' 4000 new found ability. That is why a boosted 4.2 is my current choice- its virtually undetectable at an idle.

Kimchee

and smoking stis' and modded stis' left and right....

PaulW

Would have to agree, and easier/cheaper/lighter than trying to supercharge a 4.2

PxTx

I really don't care for the aftermarket engine management required for HP 5 cyl. I also don't think it would idle too well and certainly fail emissions. There are not too many low milage turbo 20V 5 cyl around so I think I would also be into a rebuild- or a freshen up with a hone and rings at the least.

The last I knew, the pressure curve of the K24 required the engine to rev over 2000 RPM beore it made any type of boost. The SC 4.2 will have lots more power off idle. The 4.2 is actually lighter than the 5 cyle and its iron block. The 4.2 does not hang out as far as the 5 cyl which actually helps the car handle better. The 4.2 does not require an intercooler to fit behind the grill and clutter things up.

The way I see it, it ain't easier since either would be a 2Bennett conversion, it would not be any cheaper because 450 HP- with the elegance I require will cost the same no matter how you do it 5 cyl or 4.2, the 4.2 is lighter than a iron block 5 with a turbo. The SC is all aluminum and doesn't add THAT much weight.

I am open to suggestions, maybe there is something I am missing.

Paul T

Kimchee

full torque at 1850 rpms.. Garret Gt25s at about 2000... a K24 will will spool boost at nearly 3000-3200 rpms... yes it's a little bit of lag, but once it's going.. holy crap. The 4.2 aluminum block was NOT built to be a boosted motor.