Exhaust Sevo - Necessary or Not?

[NetKev92]

Hey, I'm reviving a '99 R1 for a car project which should be similar to a R6 setup on an FSAE. If I run the stock ECU and wiring harness, do I need the exhaust servo from the stock exhaust to make it run right? If I had to guess, I'd say no. I figure it's better to ask though where someone probably has experience.

Project site for those who are curious:
http://www.cardomain.com/ride/2276782

[NetKev92]

Hey, I'm reviving a '99 R1 for a car project which should be similar to a R6 setup on an FSAE. If I run the stock ECU and wiring harness, do I need the exhaust servo from the stock exhaust to make it run right? If I had to guess, I'd say no. I figure it's better to ask though where someone probably has experience.

Project site for those who are curious:
http://www.cardomain.com/ride/2276782

[Chris Lane]

We played around with and researched the R1 a bit here as we were going to build a hillclimb car before we started SAE.

The exhaust butterfly simply introduces an exhaust restriction to provide a higher spread of torque across the rev range.

We determined that we wouldn't need it as we'd be spending most of the time at high revs so it wasn't worth the weight penalty and exhaust restriction. We did this at the cost of low speed driveability (generally unimportant for a race car)

Decide where you're revs you are going to be around and where the car is racing.

[kmrobinson]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Chris Lane:
We played around with and researched the R1 a bit here as we were going to build a hillclimb car before we started SAE.

The exhaust butterfly simply introduces an exhaust restriction to provide a higher spread of torque across the rev range.

We determined that we wouldn't need it as we'd be spending most of the time at high revs so it wasn't worth the weight penalty and exhaust restriction. We did this at the cost of low speed driveability (generally unimportant for a race car)

Decide where you're revs you are going to be around and where the car is racing. </div></BLOCKQUOTE>

Our testing showed average autocross speed to be approximately 30mph. Our average RPM was approximately 7500. I would say the distribution was more on the lower end for both speed and RPM. However, our car has an engine that runs better at lower RPM and is geared as such.

My own thought is that you never want to sacrifice any power if you can.

[Chris Lane]

He's not building a SAE car.

For sure, in SAE you want a large spread of torque and gearing to match.