Forced induction for 302Z

[Z24O]

hi guys,

i was considering twin turboing the 302 in my 240z but after getting hold of a couple or garrett BB turbos off the r33 nissan skyline and mocking up in the 240's engine bay it's amazing how it goes from empty to full....and that's without all the plumbing!

anyhow i've already got the manifolding to run a single turbo upfront near the harmonic balancer but had a couple of questions ..................

 

1] what do you suggest as a suitable single turbo(motor has forged 8.5:1 pistons,edelbrock aluminium heads,eagle rods,roller cam/rockers)

2] is it worth the extra to get a twin ball bearing turbo?

3] how much slower is the boost likely to be with a single compared to twin turbos....i really want low rev torque not high rev/boost

4] internal or external wastegate?

5] would the single turbo be better than a centrifugal supercharger kit?

 

any suggestions and advice welcome,especially from anyone who's been down this path

regards

paul

[280Z28]

1) A T66 or T70 would probably be fine for your needs. Contact ForcedInductions, they'll get you better answers on that.

2) You'll be fine either way

3) If properly sized, they'll come on the same

4) External

5) If you want tq, then yes, very much so

[Z24O]

1) A T66 or T70 would probably be fine for your needs. Contact ForcedInductions' date=' they'll get you better answers on that.

2) You'll be fine either way

3) If properly sized, they'll come on the same

4) External

5) If you want tq, then yes, very much so[/quote']

 

thanks for that info

you're right the T66 and T70 compressor maps both look good for the 302,my question is how do you predict spool-up characteristics at lower revs(ie torque on the street).....should the points plotted be in the highest island of efficiency for most of the rev range?

the reason i ask is i have an rb30et in my other Z which has a T3 and is quite responsive above 2500rpm however when i looked at the T3 charts it looked ridiculously small as far as turbo choice goes,the TO4 looked better but i know these are laggy as hell on the rb30et at lower revs

this turbo choice is about as straight forward as voodoo i reckon

[CantZme]

the stock 9:1 compression should be great for off boost. As far as internals go, if ur looking for less than 500whp than u don't need more than a mildly ported stock head, a very mild cam (e303) and a gt40 intake. I would recommend a thicker mhg to bring down compression just a little to be on the safe side and arp head bolts. Internals are good for over 500whp with good tuning(aftermarket ecu). A nice twin turbo setup i've seen was using the t03's mounted on some flipped bbk headers. Turbo's are off of the turbocoupes using 2 saab 9000fmics. On a junkyard stock internal setup with a cam he is dynoing 491whp and 457lb ft.( i don't know boost levels)

[BirdmanZ]

One thing to keep in mind is that a big single will operate more efficiently at higher boost levels where as two smaller turbos will be efficient at slightly lower boost pressures.

[280Z28]

ForcedInductions should be shipping my order next week. They were EXTREMELY helpful and directed me to a new turbo I hadn't even heard of before (AirWerks S88). Ask for Jose and tell them Sam (who placed an order today) sent you.

[Z24O]

One thing to keep in mind is that a big single will operate more efficiently at higher boost levels where as two smaller turbos will be efficient at slightly lower boost pressures.

 

does this mean that the twin turbos will boost earlier(more responsive) in the rev range but run out of puff higher up the rpm scale?

thanks to you all you guys who contributed

paul

[280Z28]

does this mean that the twin turbos will boost earlier(more responsive) in the rev range but run out of puff higher up the rpm scale?

thanks to you all you guys who contributed

paul

 

A smaller "system" (single or twin) will boost earlier and let off earlier. A bigger "system" will come on later for longer. The idea is to find a system that matches your motor: ie boost is held through your main torque band.

 

If the twin system is coming on earlier than the single system, it means the twin system is smaller in an overall scale. It could just as easily go the other way if you pick a smaller single; the single would spool faster than the twins but let out earlier.

[silicone boy]

A smaller "system" (single or twin) will boost earlier and let off earlier. A bigger "system" will come on later for longer. The idea is to find a system that matches your motor: ie boost is held through your main torque band.

 

If the twin system is coming on earlier than the single system' date=' it means the twin system is smaller in an overall scale. It could just as easily go the other way if you pick a smaller single; the single would spool faster than the twins but let out earlier.[/quote']

 

 

 

I'm a Chevy dude, but if I were to do it again, I would definitely consider a big single. Mine is a 383, so I already had low end grunt. The "problem" with the twins is that they come on so smoothly, it is almost hard to tell when they kick in. No kick in the butt. The plumbing was a real pain and took me almost 2 years to fabricate and refabricate to get a decent configuration. Still, the Ford folks on the net were very helpful in providing information on twin turbos on the "cheap". I don't know if you have headers yet, but I'm sure you're aware that flipped over short headers work great (at least in a Fox body mustang--don't know about a Z.

 

Here's an argument against twins:

 

 

 

 

Somewhere under there is a small block Chevy

[280Z28]

I'm a Chevy dude' date=' but if I were to do it again, I would definitely consider a big single. Mine is a 383, so I already had low end grunt. The "problem" with the twins is that they come on so smoothly, it is almost hard to tell when they kick in. No kick in the butt. The plumbing was a real pain and took me almost 2 years to fabricate and refabricate to get a decent configuration. Still, the Ford folks on the net were very helpful in providing information on twin turbos on the "cheap". I don't know if you have headers yet, but I'm sure you're aware that flipped over short headers work great (at least in a Fox body mustang--don't know about a Z.

 

Here's an argument against twins:

 

 

[img']http://static.flickr.com/43/98091017_0eab664d65.jpg[/img]

 

 

Somewhere under there is a small block Chevy

 

Haha reminds me of this: