Turbocharging a type 4 Options

[stownsen914]

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

[iamchappy]

This is so much easier.

[stownsen914]

I'd love to just turbo my 911 motor, but the hp index for 911 turbos is not advantageous. PCA club racing classifies the 911 turbo as 210 hp/L, while the type 4 turbo is 150 hp/L. To run a 2.0L 911 turbo, I'd have to add 200 lbs to my 914 and still bump up one class. With the type 4, I can do a 1.8 or 2.0L turbo and stay in the same class at my current weight (~2000 lbs with me in the car).

[stownsen914]

So if I did this with a T4, I think I understood that it would be better to start with a 1.7 or 1.8. I did some reading over the weekend, and it looks like the 1.7 heads may be sturdy. The carb 1.8 heads have the biggest valves of any T4 (not sure if that matters since I'd probably have to increase valve sizes anyway). And don't use a motor out of a bus since the heads are more likely to be trashed from hard use.

What's the best base T4 motor to start with for a small displacement turbo?

[HAM Inc]

So if I did this with a T4, I think I understood that it would be better to start with a 1.7 or 1.8. I did some reading over the weekend, and it looks like the 1.7 heads may be sturdy. The carb 1.8 heads have the biggest valves of any T4 (not sure if that matters since I'd probably have to increase valve sizes anyway). And don't use a motor out of a bus since the heads are more likely to be trashed from hard use.

What's the best base T4 motor to start with for a small displacement turbo?

If you want to follow the small bore (max 91mm) formula then you'll need to start with 1.7 heads with 100mm registers. 1.8 heads are not the same, they have 105mm registers.

Look for a cherry pair of 1.7 heads with a 'Q' suffix. They came on 914's and 411's, but not busses.

Find a 1.7 case from a 411 or 914.

Talk to Charles Navarro at LN Engineering about a Nickies and piston & rings combo.

[stownsen914]

If you want to follow the small bore (max 91mm) formula then you'll need to start with 1.7 heads with 100mm registers. 1.8 heads are not the same, they have 105mm registers.

Look for a cherry pair of 1.7 heads with a 'Q' suffix. They came on 914's and 411's, but not busses.

Thank you, Len. I will probably keep the displacement under 2L, but I am not sure about the configuration yet. Are the 1.7 heads preferable only due to the 100mm registers for staying with a small bore? From some reading I've been doing, it looks like the ports and sparkplug position on the 2.0 heads are better. If I were to go with a 94mm bore, would 2.0 heads be a better start? I am assuming that significant porting and machining will be part of whatever I do ...

[ottox914]

If you want to follow the small bore (max 91mm) formula then you'll need to start with 1.7 heads with 100mm registers. 1.8 heads are not the same, they have 105mm registers.

Look for a cherry pair of 1.7 heads with a 'Q' suffix. They came on 914's and 411's, but not busses.

Thank you, Len. I will probably keep the displacement under 2L, but I am not sure about the configuration yet. Are the 1.7 heads preferable only due to the 100mm registers for staying with a small bore? From some reading I've been doing, it looks like the ports and sparkplug position on the 2.0 heads are better. If I were to go with a 94mm bore, would 2.0 heads be a better start? I am assuming that significant porting and machining will be part of whatever I do ...

Believe your specialists. They have your best interests in mind. The 1.7 Q has the right size register, and more "meat" in the head than any other factory casting. This gives Len room to do his magic and still end up with a head worth using. And he will do magic. Spark plug can be moved to the 2.0 location, valve sizes changed and porting done to your specifications. When he's done the part # and register size will be the only clues that these did not start out as factory 2.0 heads. But they will be much better suited to your plans.

There will be compromise here, between the valve sizes/air flow/register size you think you want, and the volcano of fire and heat you are going to subject these heads to turbo'd and track'd.