HELP! Wanna Build Twin Turbo

calereeves · Post by **calereeves** » Mon Sep 03, 2001 3:53 pm

Hey magoo, where could I find these little turbos at? you know of two for sale? As for the expeirence, I understand where your coming from, but I'm only gonna need these mods on the long straights where we race

, so I'm never gonna need to turn at any speed! As for the RX7 TTs, are they sequential or not? I think it would be EXTREMELY easy(relatively speaking of course) to hook up if it is non sequential. The two exits are on each side, right where they would need to be for dual carb blow through and the exhaust intake is in the center, the whole thing is one unit! With a porsche fanshroud, I'd have plenty of room to do this. Thanks, Cale Reeves

Magoo · Post by **Magoo** » Mon Sep 03, 2001 11:02 pm

Twin turebo? get 2 turbos off the 1000cc Suzuki 3 banger turbo ,tiny and they should have the intrnal seal required for the draw through setup.....Then run a dual carb setuo one barrel per turbo....the mazda might be adapable ,but figure on a lot of time and money and frustration to get the thing working A younster most would be better off build a 1776 1915 w/ a c/w welded crank at a mild c/r run it a while to get tha nhang of a built bug and then save up for a GOOD gear gear box cause you gonna need it A decent 1915 w/ 120 cam good heads and street tires will net you 14's,w/ dual carbs,and street tires....THEN when you have the feel of doule the stock bug hp...think about a turbo...180-200 hp can be DEADLY in inexsperienced hands think seriously about suspension upgrades please!!!! A young VW friend runs a stock 1641 and duals in a lightened early 60's sedan a runs lowwww 16.' you may be suprised whatrt a list of cars that little poop box will humble ...Good luck

Ross · Post by **Ross** » Mon Sep 03, 2001 11:08 pm

I agree, the 94mm barrels are NOT too thin the only possible drawback is the fin area is not as great as 90.5s.

Cam · Post by **Cam** » Sat Sep 08, 2001 2:23 am

*grr* thank god VW's are more reliable than computers!

jerry, what brand 94's are you using? All the sprint car guys down here run 94's and are replacing them pretty frequently due to blow by at the case end. Then again they run at 10,000RPM each weekend and have seriously long stroke engines.
I guess it's a personal preference thats all.
As for the RX7 set-up, how do you mean sequential? I've never worked on rotary turbos before so it would probably be best to call up a mazda tuner near you and ask them.
Cam

calereeves · Post by **calereeves** » Sat Sep 08, 2001 7:31 am

sequential means that there is a large one and a small one. The exhaust spools up the small one quicker and provides boost, then the larger one kicks in and brings the major power.(in a nutshell)

Jerry D · Post by **Jerry D** » Sat Sep 08, 2001 8:13 am

<BLOCKQUOTE>quote:<HR>Originally posted by Cam:

*grr* thank god VW's are more reliable than computers!

jerry, what brand 94's are you using? All the sprint car guys down here run 94's and are replacing them pretty frequently due to blow by at the case end. Then again they run at 10,000RPM each weekend and have seriously long stroke engines.
I guess it's a personal preference thats all.
As for the RX7 set-up, how do you mean sequential? I've never worked on rotary turbos before so it would probably be best to call up a mazda tuner near you and ask them.
Cam<HR></BLOCKQUOTE>
I just run Mahles....
The few Midget/sprint car racers that still run VW based cars here in the states all run Autocraft engine cases,cylinders, and heads with a ton of compression on methanol fuel
And a complete teardown and rebuild is done after each weekend of racing if not sooner. Just to keep the edge over the competition. The abuse that is put on a race motor far excedes anything I can attempt to reproduce on the street. A good solid run with with a street setup turbo max's out at about 6000 rpm. That is a 11:90 1/4 mile.

My guess would be that they would have the same problems with a stock set of 85.5's.

Jerry D...

Cam · Post by **Cam** » Sat Sep 08, 2001 8:25 am

yeah, the midgets down here run mahles, scat cranks type 1 cases etc...
A guy down the road had a turbo 2332 street engine but was'nt satisfied with the cooling around the fins on the barrels so he went back to 90.5's just to be safe and also found blow-by around the case when he pulled off the 94's.
What are your thoughts on the cooling fins issue?

Jerry D · Post by **Jerry D** » Sat Sep 08, 2001 8:28 pm

I haven't had any problems yet....Tomorrow I will measure the fins on a set of 94's and compare them to 90.5's. I really don't think there is going to be much of a differance.
I have also been considering drilling a series of small holes thru the thickness of the fins to give them more surface area for cooling. I had an old Bultaco dirtbike years ago that had holes in the fins and a longtime racer told me that it improved the cooling....I still need to do a little more homework before i'll be convinced that it's worthwhile.
Is the guy down the road from you running a stock diameter crank pulley or a so called "Power pulley". Just curious.
Jerry D...

<BLOCKQUOTE>quote:<HR>Originally posted by Cam:
yeah, the midgets down here run mahles, scat cranks type 1 cases etc...

A guy down the road had a turbo 2332 street engine but was'nt satisfied with the cooling around the fins on the barrels so he went back to 90.5's just to be safe and also found blow-by around the case when he pulled off the 94's.
What are your thoughts on the cooling fins issue?<HR></BLOCKQUOTE>

Cam · Post by **Cam** » Sat Sep 08, 2001 10:57 pm

Cool, let us know if it helps.
Was a standard sized pulley, he used the car everyday.

Jerry D · Post by **Jerry D** » Sun Sep 09, 2001 11:46 pm

Ross,
After reading your post about the fin area it got me thinking.
I measured the od of the top fin on a 90.5 and a 94 Mahle cylinder and the differance is minimal.
90.5 top fin od 9.55
94 top fin od 9.62
90.5 cylinder od at top 8.85
94 cylinder od at top 8.98

* the fin od is as accurate as one could expect to get when measuring a cast surface.

My thoughts are that you might as well use 94's for that extra kick in the pants.

Jerry D...

<BLOCKQUOTE>quote:<HR>Originally posted by Ross:
I agree, the 94mm barrels are NOT too thin the only possible drawback is the fin area is not as great as 90.5s.<HR></BLOCKQUOTE>

[This message has been edited by Jerry D (edited 09-09-2001).]

Sharkey · Post by **Sharkey** » Mon Sep 10, 2001 6:24 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Jerry D:
I disagree with you about not using 94's. The wall thickness of 94's is every bit as thick as it needs to be for many miles of "spirited driving" so to speak.<HR></BLOCKQUOTE>
That isn't the main concern. With 94mm jugs, you can't run 10mm headstuds, which many people claim are necessary to keep your heads from flying off when it comes to the sorts of combustion chamber pressures we're talking about.

Sharkey · Post by **Sharkey** » Mon Sep 10, 2001 6:28 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Magoo:
Twin turbo? get 2 turbos off the 1000cc Suzuki 3 banger turbo ,tiny and they should have the intrnal seal required for the draw through setup.....<HR></BLOCKQUOTE>

AFAIK, the turbos you are talking about will NOT have the necessary seals for a draw-thru system. They were used on a blow-thru EFI system and never had to deal with a pressurized air/fuel mixture-- only air.

Sharkey · Post by **Sharkey** » Mon Sep 10, 2001 6:33 pm

The biggest concern with running dual turbos instead of a single, larger one is "space". If you have enough room for the second turbo, then it might be worth a try. OTOH, you'll have to deal with twin wastegates, twin oil feeds, twin oil returns, etc. The complication goes up.

My suggestion is to start with a basic kit and drive the finished product for a while. You will probably like it enough and forget all about twin turbos. Or, you can use it as a testbed for future turbo projects.

Jerry D · Post by **Jerry D** » Mon Sep 10, 2001 8:27 pm

We have been running Berg so called original VW 8mm studs in turbo motors (W/ case savers)at 15lbs boost for quite a few miles with no problems.
I have asked on this forum and others about using 8mm or 10mm and 4 or 6 stud per cylinder. Most people have answered 8mm even in full race situations.
I'm getting ready to build my latest and greatest (to date) turbo EFI motor and I and I am still baffled by the 8mm/10mm controversy.

I'm sooo confused!
Jerry D...

<BLOCKQUOTE>quote:<HR>Originally posted by Sharkey:

Originally posted by Jerry D:
I disagree with you about not using 94's. The wall thickness of 94's is every bit as thick as it needs to be for many miles of "spirited driving" so to speak.<HR></BLOCKQUOTE>
That isn't the main concern. With 94mm jugs, you can't run 10mm headstuds, which many people claim are necessary to keep your heads from flying off when it comes to the sorts of combustion chamber pressures we're talking about.

danimal · Post by **danimal** » Mon Sep 10, 2001 10:54 pm

>>>We have been running Berg so called original VW 8mm studs in turbo motors (W/ case savers)at 15lbs boost for quite a few miles with no problems.<<<

yeah, what he said

i'm at around 5k miles on my turbo motor(15psi) with factory 8mm head studs.

i remember when this subject came up on the old clf... mark herbert and steve arndt had some pretty sad tales to tell about non-factory 8mm head studs, but then there was this:

"I have 8MM german head studs in my 1914 w/ N.O.S. I have split barrels & blown holes on the heads, but I have never had a stud problem. I torque them to 26 lbs too. (n/t) (manxracer1-shawn)"

i think that there are a lot of people running those crappy 10mm head studs w/94's; some of 'em turn down the jug at the bottom, and i seem to remember hearing about a special size of case saver(???).

dan
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