SUPERCHARGER!

[Lyle's GTP]

With new supercharger designs you get boost instantly. ie. The Whipple style supercharger, next best being the Eaton style, then the Centrifugal type. With a supercharger you can develope PSI at low RPM and bring up the CFM through the RPM range. Any excess pressure can be by-passed through a blow-off valve. The CFM will be constant as long as your PSI is up. As long as you keep your pressure regulated you should be OK. If you use a turbo it takes time for it to spool-up because you need the CFM output from your exhaust to turn the thing. When you punch it you will need alot of N/A power before you get the boost.

Turbo's are much higher maintenance anyway. Due to the high temps, they practicaly need there own oil cooler to not melt-down under any prolonged conditions. They recieve so much heat from the exhaust system plus they are spinning so fast there is a hugh amount of frictional heat developed within the bearings. At least with the supercharger you only have the bearing heat to worry about. Also sinch the Blower design (commonly) is much better at dissipating heat that helps too.

I see no preformance/durablity advantages to using a turbo on anything but Ricers and Diesels.

Lyle

[grandprixgtp_91]

Yeah i really dont want a turbo at all. plus ive already got this supercharger and im not going to go buy anything else. i dont think i am going to be using a blow off valve , if there is a problem with this tell me! also i hear that this M-90 produces 12-14 psi of boost so i dont think ill find a turbo that does that. im hopping ill get over 100 hp off of it if i tune it properly, maybe more if im lucky! i still just need to figure out the computer and fuel shit.

Jake

[brian89gp]

I see no preformance/durablity advantages to using a turbo on anything but Ricers and Diesels.

Lyle

There are plenty of 9 and 10 second turbo Buick, Mustang, and Supra owners that will argue that point. Not to mention the twin turbo Corvette and Vipers. And me.

And turbo's use a floating bearing design so there is very little heat that comes from bearing friction because there isn't that much friction in the first place. Most the heat comes from the exhaust and the small remainder will come from the actual act of compressing air.

Jake, boost is not a good measurement of a turbo/sc's potential, CFM is what matters. In simplest form boost is a measure of how inefficiently the engine breaths. With a turbo 300 at the wheels on a stock DOHC with around 8psi is about normal, minus some for the M90 and thats what you got. And a M90 is a fairly good choice for this motor, just be sure to make certain the engine can breath on both the intake and exhaust (CFM makes power, not boost)

[Lyle's GTP]

There are plenty of 9 and 10 second turbo Buick, Mustang, and Supra owners that will argue that point. Not to mention the twin turbo Corvette and Vipers. And me.

I was talking prolonged use, not drag apps. I don't factor in durability as a main issue when dealing with 1/4 mile cars. That's why alot of the Merlin and Donoven blocks don't even have water jackets. Run 'em for 2 minutes and shut them down.

lyle

[Dave]

I can list dozens of turbo mustang guys who've had their turbofords outlast their supercharged counterparts, namely the thunderbird turbocoupe/supercoupe...

[pocket-rocket]

I like the thought of a turbo being easier and cheaper to rework to get more power out of it, and also being easier to intercool (because we all know detonation is bad). Now with the M90 off of the SC Tbird, at least you have that option too.... Then look at our other problem, FWD. Dump an M90 on there and I bet you can kiss good traction goodbye as it flys out the window. At least with a turbo, it kicks in after your moving and have already established traction. What good is power if you can't get it to the ground effectively?

[grandprixgtp_91]

Yeah that was one of my big concerns too, and frying clutches very fast. i mean i couldnt stop spinning the tires before now if i supercharge it its really gonna spin them, well right now ive only got p225/50R16 tires on it but the factory size is P245/50R16 so when i get the car back on the road i will put those back on or P255/50R16's on it, whatever i can do to get traction. i guess ill have to learn how to start off a race without spining them after its supercharged. another option i have is to make the car all wheel drive and i could do it too because the whole thing is ripped apart but i think that would be way to much work and put to much weight on the car, but wouldnt it be nice!oh well lots of work ahead of me here!

Jake

[Fierobsessed]

I know turbo's have more potential for power. I don't really care about that. I like the SC because:
1. To the best of my knowlege, it has NEVER been done before.
2. Look at the 4.6L DOHC SC Cobra engine
3. The blower has proven to be good for 11 second passes, How much faster would I want to go? 11's is plenty fast.
4. The blower has no real drag (1/3 Horse) when the bypass is open, In other words, excellent gas mileage. Does any turbo open its wastegate while crusing to relieve the exhaust pressure?
5. That classic hot rod engine look, people tend to notice a blower sticking out of your hood. (or sideways out of a decklid in my case )
6. Have you ever heard an Eaton SC howling along? The sound turns heads, and draws crowds.
7. The flow characteristics of a blower make a DOHC engine much more useable at lower RPMS (daily driving) and still great upstairs too.
8. The math. Figure a 2:1 ratio blower to crank. Engine flows 102 cubes per rev,(204 cubes devided by 2) the blower flows 180 per crank revolution. This is almost twice the amount of air the engine is supposed to take in. Thats theoretically about 12 PSI of boost maximum. The blower is designed to turn 14,000 RPM's and the engine is designed for about 7,000. Theres your 2:1 ratio again! It just works out good.

The 3800's ports are much smaller then those on the 3.4 DOHC so boost tends to back up more causing the air to heat and lead to detonation. Importantly, the exhaust ports on my 96 DOHC are HUGE. Witch is great for boosted engines to get the hot gasses out of the chambers witch otherwise would cause detonation. Basically I just see so many advantages to having the blower on the 3.4 DOHC.

Oh, a couple more teasers. The crate engine (still in the origional crate) with the blower sitting on it.

[Fierobsessed]

Jake, boost is not a good measurement of a turbo/sc's potential, CFM is what matters. In simplest form boost is a measure of how inefficiently the engine breaths.

This is true up to a point, Boost is still viable as potential power. I hinted this in my previous post, Neglecting all restrictions, my blower will shove almost twice as much air as the engine could theoretically take, equating to almost 12 PSI. Where boost becomes a measurement of inneficiency is when it goes beyond this theoretical number. At least for my engine. If Im pushing 17 PSI, somethings holding 5 PSI worth of my air back. Not to mension the 28 crank horsepower it takes to make the extra 5 PSI @6000 RPM's. Innefficiency strikes twice in this case.

[Lyle's GTP]

Fieroobsessed wrote:

Basically I just see so many advantages to having the blower on the 3.4 DOHC.

Here Here!

Lyle

[Lyle's GTP]

Man, I hope you will devulge your 3.4 blower secrets to me when I build my blower.

Lyle

[brian89gp]

4. The blower has no real drag (1/3 Horse) when the bypass is open, In other words, excellent gas mileage. Does any turbo open its wastegate while crusing to relieve the exhaust pressure?

There isn't really any exhaust pressure to relieve during cruising. Mine cruises within 5kpa manifold vacuum as does a NA engine. You are right, a M90 will definately be fun.

[Anonymous]

1) What are you expecting to get in hp? tq? 1/4mi?
2) What are you going to do about a transmission?
3) What kind of car is it going into?

[Gemmer]

Im gonna assume by his name its a fiero

[Fierobsessed]

right on. Into a Fiero.

I'm shooting for 350 horses but would still be quite happy with 300. I don't want more then 400.

1/4 Mile? probably low 12's into wherever in the 11's. I'll be just as happy if its anywhere in the 12's. Fiero's are pretty good with traction.

Transmission will either be a Standard Fiero 5 speed Getrag, or I might build it up with a 3.94 ratio from a Quad 4 transmission. Nothings set in stone till its time to put this engine in. Im building a nice motor, but have no real plans for it. Kind of a take the time and do it right tactic. This is over a year into the project. When I actually learn how to tig weld I will finish the manifold.