Out with the old...in with the new...Britain's Racecar Development, Subaru Engine, Lotus Suspension! Time to go racing! Options

[Britain Smith]

For those who don't know me or the car, I have a '74 914 that is a dedicated AX car. It previously had a high compression 2.7 6-cylinder motor and made 205hp/205ft-lbs at the wheels. This set-up wasn't all that bad considering that it won the 2008 and 2009 914 Shootout events, however the quest for more speed continues.

Here is the car in the 2010 season trim.

(IMG:http://www.914world.com/bbs2/uploads_offsite/dragracevws.com-364-1291656786.1.jpg)

I have recently sold the 2.7L 6-cylinder engine and all the remaining 914/6 conversion parts. I have used the proceeds to fund the conversion to Subaru power. Now most would say that a Subaru conversion can be done on a budget, however I have found that the money goes flying out the window when doing something like this.

Regarding the engine...logical choice would be to go for a EJ257 2.5L USDM STi engine. However, all the SCCA rules for AX are built around displacement which in turn dictates the minimum weight. Therefore, I have gone with a JDM STi version8 Spec-C engine which is a 2.0L, twin-scroll, hand ported/polished, 8500rpm animal. I will get slightly less hp and torque numbers than the 2.5L, but save 150lbs of weight.

[Britain Smith]

Another thing to consider from them is their vehicle speed sensor. I have found that my engine ECU requires a vehicle speed sensor for the active valve time to function. I ordered mine today.

-Britain

[charliew]

Another thing to consider from them is their vehicle speed sensor. I have found that my engine ECU requires a vehicle speed sensor for the active valve time to function. I ordered mine today.

-Britain

My son has been hotrodding his 04 sti since he got it new. He's a mechanical Engineer with our hotrodding exposure from my and his toys. We aren't track guys though. I started with a new 02 wrx motor in a 901 tail dragger dunebuggy but decided the 914 was a better way to go. I have been planning and scrounging parts for a long time and soon may get to start the real deal. When I studied the smartcar vss a few years ago I bought one but my understanding it is only to make sure the car is in motion, it will not replace the speedo feedback. I guess you know what you are talking about on needing the two waste gates. My thought is the inlet side using two waste gates might reduce the surge of the turbo better but the pulses from each exhaust port would seem to me be better controlled after the turbo wheel rather than before to get the quickest spool time. You are doing great though and will be a very valuable source on what works at high rpm in the 914 high g suby configuration. The suby uses more oil than you will think at high rpm and high oil temps so monitor it very carefully. Now that the twin scroll exhaust is removed I would tackle the oil pan and try to get as much more capacity as you can. The oil pickup is a very critical spec on the suby motor, there is a lot of variation in the oil pan tp pickup clearance. The external oil cooler is really necessary, get a oil temp sender and good gauge. The good thing is it's a race car and you can change over heated oil pretty regularly. You also may have considered a turbo blanket I hope. Are you going to learn to do open source programming on the oem ecu also? I am anxious to see if your radiator is going to be big enough. If the boost is laggy you might want to check the exhaust back pressure at the turbo. The exhaust on my son's sti is at least 3.0 all the way with straight through muffler and no cat. Your exhaust is shorter though. I do wish you had gone with the suby tranny also.

[Britain Smith]

When I studied the smartcar vss a few years ago I bought one but my understanding it is only to make sure the car is in motion, it will not replace the speedo feedback.

Yea, that is my thought as well. However, using the Small Car Performance speedo sensor kit I should be able to get relative speed numbers and I can feed that into my AIM dash for datalogging.

I guess you know what you are talking about on needing the two waste gates. My thought is the inlet side using two waste gates might reduce the surge of the turbo better but the pulses from each exhaust port would seem to me be better controlled after the turbo wheel rather than before to get the quickest spool time.

The wastegates go before the turbo and the blow-off valve goes after the turbo. I need two wastegates because I have cylinders 1 & 3 and 2 & 4 entering the turbo separately (twin-scroll) and the two wastegates will keep the exhaust pulses independent. Wastegates control the amount of exhaust gases that go to the turbo and therefore control the boost pressure. The blow-off value is between the turbo and the throttle body to reduce surge of the turbo when the throttle is closes...the pressurize air needs somewhere to go.

You are doing great though and will be a very valuable source on what works at high rpm in the 914 high g suby configuration. The suby uses more oil than you will think at high rpm and high oil temps so monitor it very carefully. Now that the twin scroll exhaust is removed I would tackle the oil pan and try to get as much more capacity as you can. The oil pickup is a very critical spec on the suby motor, there is a lot of variation in the oil pan tp pickup clearance. The external oil cooler is really necessary, get a oil temp sender and good gauge. The good thing is it's a race car and you can change over heated oil pretty regularly.

Yes, I am also concerned about oil pick-up under the conditions that I run. I have an Accusump plumbed in and will be address the oil pan after the engine is running on the dyno.

You also may have considered a turbo blanket I hope. Are you going to learn to do open source programming on the oem ecu also? I am anxious to see if your radiator is going to be big enough. If the boost is laggy you might want to check the exhaust back pressure at the turbo. The exhaust on my son's sti is at least 3.0 all the way with straight through muffler and no cat. Your exhaust is shorter though. I do wish you had gone with the suby tranny also.

Yes, I have considered a turbo blanket or heat shield...we shall see how things go on the dyno.

Yes, I am using Open Source tuning...however this will be done at Cobb Tuning.

The exhaust is 2.5" all the way back and with the smaller turbo, it should be fine.

I might be changing to a different trans, we shall see how long the 901 lasts.

-Britain