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

[zig-n-zag]

FAT Performance does install 911 oil piston squirters in Type 4 cases, check with them.
I read somewhere that when using twin-plug ignition, there are more gains in power for smaller bores than with larger bores. It might have been written in the B Anderson 911 Handbook, or maybe in Up-Fixin...going by memory on this...
I bought ARP thru bolts and ARP head studs. Jake recommends the head bolt torque be 24lbs, no mention of the case thru bolts. Gene Berg raised the case torque on Type 1s by spot-facing all the bolt holes and using thicker, hardened washers. An old article about engine builder John Zeitler increased thru bolt torque to 40lbs, perimeters 35lbs.

[stownsen914]

I read somewhere that when using twin-plug ignition, there are more gains in power for smaller bores than with larger bores. It might have been written in the B Anderson 911 Handbook, or maybe in Up-Fixin...going by memory on this...

You're right about B. Anderson and the twin plug, but I think that was for 911 engines. The dual plugs make a lot of sense on the 911 due to the hemispherical combustion chamber shape, and even more so on high compression 911 motors, since high-domed pistons make the situation even worse.

I thought that dual plug didn't have the same advantages for type 4's since they have flatter combustion chambers and pistons (and like many other engine types that also don't get much benefit from dual plugs). But maybe I'm wrong on that?

[HAM Inc]

I read somewhere that when using twin-plug ignition, there are more gains in power for smaller bores than with larger bores. It might have been written in the B Anderson 911 Handbook, or maybe in Up-Fixin...going by memory on this...

You're right about B. Anderson and the twin plug, but I think that was for 911 engines. The dual plugs make a lot of sense on the 911 due to the hemispherical combustion chamber shape, and even more so on high compression 911 motors, since high-domed pistons make the situation even worse.

I thought that dual plug didn't have the same advantages for type 4's since they have flatter combustion chambers and pistons (and like many other engine types that also don't get much benefit from dual plugs). But maybe I'm wrong on that?

As for the twin plugs it's the other way around; the extra plug benefits larger bores more than smaller bores.

On 911's the second plug is advantageous because the piston dome interferes with the flame front. Putting a second plug on the opposite side of the chamber cuts down on detonation. This is a typical issue with true hemi chambers.

A second plug on a T4 is a royal PITA to deal with. Gets pretty crowded and hot on the bottom of the engine. The plug wires routing is a challenge.

All of those challenges can be (and have been) overcome, but with a small bore (90-91mm) wedge chamber using a flat top or even dished piston, the second plug will not be needed.