Turbocharging a type 4 |
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Turbocharging a type 4 |
stownsen914 |
Oct 12 2016, 02:04 PM
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#1
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Senior Member Group: Members Posts: 928 Joined: 3-October 06 From: Ossining, NY Member No.: 6,985 Region Association: None |
I have heard the conventional wisdom that "you can't turbocharge a type 4 successfully." Is it just difficult, or can it really not be done well? I'm tossing around the crazy idea of turbo'ing a type 4 for PCA club racing, to put in the chassis in my avatar. My 6 in its current configuration is not competitive, so I can put a bunch of money in that, or do something different. I like a challenge, so why wouldn't the following work?
- 1.8 or 2.0 type 4 as a base. I would keep displacement stock or close to it. - EFI for induction - Properly sized intercooler and huge oil cooler - A good aftermarket cooling fan - Would be dry sumped - I would work with a knowledgeable builder or shop to build the engine. I am not so familiar with type 4 race modifications, but presumably this would include reinforcing the bottom end, using Carrillo, Pauter, etc. rods - Obviously the heads would need to be reworked for flow and possibly reliability If I do the above, could a type 4 be built to withstand 15 psi of boost and make 350 hp reliably? Scott |
HAM Inc |
Oct 12 2016, 06:53 PM
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#2
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
It can be done, but the heads are indeed the weak point, specifically, the combustion chambers in the areas positioned directly above the exhaust ports.
Take a look at the way the port cuts directly beneath a significant area of the chamber. That area is very thin. When exposed to high pressure and high heat it droops into the hollow space that forms the port, anywhere from a few thousanths to half a milimeter in extreme cases. It only takes a few thousanths to blow the jug seal. This droop is a problem on N.A. engines of modest CR's when temps get high enough in the presense of steady high revs at full throttle. The aluminum is pretty soft at the egt's that peak power demand -1225-1250. Turbo's like high egt's, and they generate a good deal more cylinder pressure than NA engines. My suggestion for making it work is to keep the bore as small as possible, the stroke as long as possible and the revs as low as possible. Think really low speed torque. If I were building a turbo T4 I'd look for a pristine pair of 1.7 Q heads and follow the above blueprint, with a max bore of 91mm. A fellow on here did a pretty good job with his turbo T4 engine. He followed that blueprint. He didn't cook the heads, but he did hurt it with a mechanical overrev. |
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