supercharging z31

[iaconsultants]

My suggestion on Turbo systems is read some of Corky Bell's books, he has done a lot with Z's and old RX7's in the past (also many other cars and planes). Based on my experience (many years of turbos and superchargers) the Z engines are better complimented with the use of Turbos then would be with the supercharger. Also to commenton someones statement that a screw supercharger adds heat, well based on the ones I have done it does not and I am currently running one on one of my vehicles for the past 6 or 7 years (turbos add a huge amount of heat compared to superchargers). If youwant some help figuring out what you need to do with the supercharger on a Z engine to get what you want, then you can always read some books, ask questions, and feel free to send me an email and I will help as I can. I only have like 20+ years of playing around with forced induction from 4 cylinders to some V10's. But really read some of Corky's books they are very good and he really knows his stuff.

[MIBPreacher]

Titaniumbmx, if and when you get this installed, will you take some pics and jot down how you got everything hooked up? I took a look on ebay and they are very reasonable priced. I know everyone here is pro turbo and all that but wouldnt someone putting this on their Z just be oozing the hybridZ spirit? We can put the taurus fan on why not the thunderchicken supercharger? I like the idea as its cheaper then doing the turbo route by a long shot.

 

t'bmx, I wonder where your going to get the pulley from?

[titaniumbmx]

yeh i got a machinist in mind for that one my friend mike is a wiz:mrgreen:

[COZY Z COLE]

titaniumbmx, good luck on your quest.... This has been an "interesting" thread to read.

 

 

LARRY

[mtcookson]

Also to commenton someones statement that a screw supercharger adds heat, well based on the ones I have done it does not and I am currently running one on one of my vehicles for the past 6 or 7 years (turbos add a huge amount of heat compared to superchargers).

 

Screws superchargers have around a 70-80% adiabatic efficiency (heat efficiency) as do centrifgual superchargers and turbochargers. Turbochargers do not add a huge amount of heat compared to superchargers. If they did, adiabatic effiency would be much, much lower. Like for instance... a roots supercharger. They are around 40-50% if I remember correctly. That's how inefficient a roots is.

 

That is why I recommend screws superchargers over all of the other superchargers. The reason a turbocharger is then more efficient than a screws is due to parasitic losses.

 

Back to the exhaust... even with the heat of the exhaust, a turbocharger still has an adiabatic efficiency upwards of 80%. The heat of a turbocharger system is highly overrated. Yes... heat radiated from the exhaust can cause power loss if not setup properly. Proper steps need to be taken to keep the keep where it needs to be... in the exhaust. When done right, a turbo can be way more efficient than the supercharging methods.

 

 

titaniumbmx... if you do the centrifugal setup you should try doing a sort of variable pulley setup. I've had the idea for a while but have no way of trying it. Basically... if you've ever seen the way a snowmobile or a Honda Odyssey/Pilot works (off road vehicles, not the van and suv) that would be a cool setup to go with.

 

If you could figure out a way to time the pulleys to where at... say 1,500 rpm or so they spun the supercharger to its peak then kept it at its constant peak to your engine's redline... I bet the power output would rival a screws supercharger very easily. That could easily be the ultimate supercharger setup if it can all be timed right.

 

Maybe sometime down the road I'll be able to try it out myself and see what I can come up with. Just have to find the pulleys and figure out the spring setup (or better yet do something electronic).

[veritech-z]

mtcookson, are you describing some kind of centrifugal clutch, like the way those mini-chopper motorcycles work?

[mtcookson]

Kind of... it would have to be modified and reversed to where the input/drive pulley is the larger one and the output/driven is the smaller one. In most CVT setups the smaller one (starts small, goes big) acts as a clutch by being open enough to lets the belt ride between the sides when at idle then when the rpm increases the sides come together.

 

I haven't been able to mess with one yet but I'm pretty sure if you put a spacer in to take away its clutching ability, you can reverse the input and output so that you can keep the supercharger at max RPM throughout the rev range.

 

You have the right idea though... those pocket bikes use the CVT setting I'm thinking... just needs reversed and modified. If you could make it all work the benefits would make a world of difference.

[Guest floyd084]

hey, im thinking of doing the same thing to my 86 n/a. I was looking on ebay and found some to4e-54 i was looking at the compressor maps for the 54 trim and it seems that ill need to spin it at about 70k rpm to make 8 psi (dont really plan on going over that) i found an online timing belt maker that can make gears for the setup( www.sdp-si.com/estore/CoverPg/Pulleys.htm ). i know i can make the compressor spin at 70k rpm at redline. what i want to do is add either an a/c clutch to controll the sc rpm or add a valve of some sort on the intake to limit boost. any thoughts?

[veritech-z]

TO4E-54 sounds like turbo nomenclature to me, is that a centrifigal supercharger? As for the AC clutch idea, that would be an on/off affair, so you would be running with no boost, or whatever boost you would normally have at that rpm. I've heard mercedes has some kind of electric clutch on their new superchargers, but i'm not too clear how those work...

[Guest floyd084]

yeh that is a turbo, i plan on using the compressor side to save money. otherwise i woudl jsut go out and buy a vortech or like unit. ive heard that an a/c clutch is very similiar ot the merceds clutch, thats how i got the idea to use the ac clutch. is it possible to jsut bleed off the extra boost through a valve.

[Guest ZFury]

Yeah, you can use a Blow off valve. Those Merc. chargers with the clutch look neat. I was thinking about getting one and removing the clutch if possible. But didnt know if it was really possible.

[mtcookson]

hey, im thinking of doing the same thing to my 86 n/a. I was looking on ebay and found some to4e-54 i was looking at the compressor maps for the 54 trim and it seems that ill need to spin it at about 70k rpm to make 8 psi (dont really plan on going over that) i found an online timing belt maker that can make gears for the setup( www.sdp-si.com/estore/CoverPg/Pulleys.htm )[/color']. i know i can make the compressor spin at 70k rpm at redline. what i want to do is add either an a/c clutch to controll the sc rpm or add a valve of some sort on the intake to limit boost. any thoughts?

 

Lets say the engine redlines at 7,000 rpm and you need the compressor to spin at 70,000 rpm. Without any other internal gearing, you would need a 10:1 pulley ratio... which is a 10 inch drive pulley and a 1 inch driven pulley. Cut that in half and you'll have a 5 inch drive pulley with a .5 inch driven pulley. The former setup requires a pulley that is way too big, the latter setup requires a pulley that is way too small.

 

If I'm looking at the right maps, it'll take more RPM than that to reach 8 psi. Even if the max was 70k rpm, that's still much higher than you want it to spin. If you absolutely want a centrifugal supercharger, I'd just get a centrifugla supercharger. Most decent sized belts aren't going to accept a .5 to 1 inch pulley very well.

 

Plus... the driven pulley and shaft would need to be perfectly balanced because all of that will be spinning at 70k rpm (if that were the limit). I think its actually closer to about 80,000 rpm, which only makes things harder.

 

Unless you can do some sort of gear box on the turbo compressor, then do the pulleys... I think you're going to be looking at more work than you'll want to do and potentially more money than you'd spend on a real centrigual supercharger.

 

That's how I see it.

[Guest ZFury]

I dunno' what the RPM's needed will be. But those chargers on the 3.8L fords prolly did around 5psi and still needed a actuator wastgate. So you shouldnt need much more than what was stock for your 3000cc motor. (my 2 cents)

[mtcookson]

The roots superchargers have a recirculation valve so that there is no boost while idling.

[Guest ZFury]

Recirculation valve is what I ment by waste gate. Its the same except the valve isnt in the exhast but in the intake and it dumps air from the high pressure side into the low pressure intake. How you operate that valve is all up to you.

[mtcookson]

Yes, I know. I just stated that it doesn't matter at what pressure you're running you need the recirculation valve so that it doesn't give boost at idle.

 

A centrifigal likely won't need one. It should be spinning slow enough at idle that it won't create any boost. That's why centrifugal superchargers actually have a sort of lag like a turbo does... even though they are belt driven.

[Guest ZFury]

Having boost at idle shouldnt be a problem.

[Guest floyd084]

Lets say the engine redlines at 7,000 rpm and you need the compressor to spin at 70,000 rpm. Without any other internal gearing, you would need a 10:1 pulley ratio... which is a 10 inch drive pulley and a 1 inch driven pulley. Cut that in half and you'll have a 5 inch drive pulley with a .5 inch driven pulley. The former setup requires a pulley that is way too big, the latter setup requires a pulley that is way too small.

 

If I'm looking at the right maps, it'll take more RPM than that to reach 8 psi. Even if the max was 70k rpm, that's still much higher than you want it to spin. If you absolutely want a centrifugal supercharger, I'd just get a centrifugla supercharger. Most decent sized belts aren't going to accept a .5 to 1 inch pulley very well.

 

Plus... the driven pulley and shaft would need to be perfectly balanced because all of that will be spinning at 70k rpm (if that were the limit). I think its actually closer to about 80,000 rpm, which only makes things harder.

 

 

the gear ratios i have now are:

diameter in inches

pulley 1 is actually two different pulleys on one axel.

the 5 inch and 1st 1.2 inch are connected and the 4 inch and turbo 1.2 inch are connected

 

 

-------------------Crank-----pulley1------pulley1-------Turbo

Pitch Diameter ------5--------1.2 ----------4 ----------1.2

Circumference ----15.707-----3.76 -------12.56--------3.76

RPM ---------------6200-----25000------25000------83333.33

 

 

 

i do understand that it will need to be balanced very well, but i figure a vortech unit cost around 1500-2000, im sure i can get this done for under a grand. im not even sure if i need 8 psi, maybe 5. im trying to get my n/a motor to about 230-240 horse, but the only way ill reach that is with some sort of boost. and im NOT doing nitrous.

[mtcookson]

There you go, that should definitely work... however, you may need more than 5 psi to reach your power goals. You might get what you're aiming at, at redline but this won't help you much. Since the boost of a centrifugal s/c is linear, you need a higher peak boost to have more boost in the mid range.

 

At only 5 psi, you'd probably only see roughly 1 psi at the engine's peak torque which would hardly be any fun. I know a guy with a turbo Maxima (VG30E) running a Toyota CT26 turbo that is making over 300 ft. lb. of torque at 2,800 rpm but just over 250 hp (if memory serves).

 

You should also look into turbocharging your car using stock Z31 Turbo components. I bet you could easily stay under $1,000 and have better overall performance. I did something similar using Z31 Turbo parts on my Maxima and got it running on $1,500. That included quite a bit of custom work as well. Yours wouldn't need any. On a poor tune, leaky exhaust, and very restrictive intake I made about 210 whp and I think 230 wtq with an 85 Z31 T3.

 

I'd get the turbo crossmember and various neede swap parts, put a 3 inch exhaust on it, and good flowing intake, run it at about 7 psi or so and call it a day. You'll have much more low end torque, which would make it a much more pleasant car to drive on the street.

 

Like I mentioned above, on a very bad tune with leaky exhaust and a poor intake I still manage a hair under 30 mpg. I know with fixes to those problems I'll easily surpass 30 mpg and make much more power to boot.

 

I can gauranty that you would be overall more pleased with the turbo setup than you would with the s/c setup and you wouldn't be spending any more money doing it. It might take a bit more work to pull off... but the results would be well worth the effort.

 

Here's an excellent site for the N/A to Turbo swap. http://www.redz31.com/pages/turbo.html

 

 

If you absolutely want to go with the s/c... I think you're definitely on the right track so far but like I mentioned above, you might have to run some more boost than you planned on for the power you want mostly because of the peaky nature of the centrifugal s/c.

[Guest ZFury]

You should be able to get an NA to 300hp or more with cams (head work) and carbs/FI. If going nonNA, thats when you can get abnormal HP numbers. I mean, you do realize that stock 5L push rod motors were getting 300+hp stock.