Pure Motorsport: JDL Turbo BRZ Track Build

[King Tut]

Originally Posted by ATL BRZ

Got some really good laps in that I'll share very soon.

You get any lap times?

[ATL BRZ]

Originally Posted by King Tut

You get any lap times?

Yes with my slow-gps Nexus 5 and Harry's Lap Timer. Did a few gps-inaccurate 1:37's before my tires started falling off badly. They were already heat cycled out and they're now past the wear bars approaching the cords. Time for RE-71R's!

Also had fuel starvation again at T14-15 up the hill around the carousel if I wound out 4th gear at 3/4 tank. Last weekend at AMS it happened around the banking below 1/2 tank. Never happened before at AMP but the car is making more grip and pulling more lateral G's with the extra aero now. I could avoid it by short shifting into 5th and not winding out 4th gear above 6k rpms up the hill which killed my top speed and lap times. After topping off the tank with E85 it didn't starve again until 3/4 tank.

[King Tut]

Originally Posted by ATL BRZ

Yes with my slow-gps Nexus 5 and Harry's Lap Timer. Did a few gps-inaccurate 1:37's before my tires started falling off badly. They were already heat cycled out and they're now past the wear bars approaching the cords. Time for RE-71R's!

Also had fuel starvation again at T14-15 up the hill around the carousel if I wound out 4th gear at 3/4 tank. Last weekend at AMS it happened around the banking below 1/2 tank. Never happened before at AMP but the car is making more grip and pulling more lateral G's with the extra aero now. I could avoid it by short shifting into 5th and not winding out 4th gear above 6k rpms up the hill which killed my top speed and lap times. After topping off the tank with E85 it didn't starve again until 3/4 tank.

I fuel starved there as well. It really upsets the car when you are going that fast and suddenly have no throttle input. I worry about how many street miles those RE-71Rs are going to be good for. I want to see some reports on the new Kumhos as well. I am probably going to go for a stickier street rubber next time. My Michelin PSS have over 35 heat cycles on track and one 8 run AutoX, but they still feel good on track, but I am sure they have lost significant grip.

[gramicci101]

A surge tank might fix the starvation problem. I remember the tank pressurization system we used on F-16's, so I figured there must be something similar for cars that also experience high g forces. That led me to surge tanks, which led me to Ian @MAPerformance, who directed me to the above link. I don't know what kind of fuel flow these cars need in a track environment though, and I don't know if they'd work with a flex-fuel system, although E85-specific tanks were listed.

[sw20kosh]

Originally Posted by King Tut

I worry about how many street miles those RE-71Rs are going to be good for.

Friend recently did hpde weekend on his new re71r..... The outsides are more than 50% done after one weekend. He is adjusting his camber accordingly. Swapping fronts to backs he figures it will last one more weekend and then done. He is switching to NT-01 next. This is strictly a track car. Not daily driven. LOL. For comparison his Rivals lasted 5 weekends and still had tread when he took them off. Re-71 is sooooffftttt.


@ATL BRZ

[ATL BRZ]

Originally Posted by sw20kosh

Friend recently did hpde weekend on his new re71r..... The outsides are more than 50% done after one weekend. He is adjusting his camber accordingly. Swapping fronts to backs he figures it will last one more weekend and then done. He is switching to NT-01 next. This is strictly a track car. Not daily driven. LOL. For comparison his Rivals lasted 5 weekends and still had tread when he took them off. Re-71 is sooooffftttt.

I've been reading that they wear VERY quickly but I don't understand how they get a 200 treadwear rating?!?

[DocWalt]

R compounds with tread? I think the RE71R will wear a lot better with proper camber, but it's still soft compared to the older spec Rivals or the RE11.

[gramicci101]

Originally Posted by ATL BRZ

I've been reading that they wear VERY quickly but I don't understand how they get a 200 treadwear rating?!?

It's in their interest to be a 200tw tire so autocrossers can buy them, so I'm sure they padded the stats a little. Treadwear is such a subjective number anyways that they can get away with it.

[Jonsey]

Originally Posted by ATL BRZ

Also had fuel starvation again at T14-15 up the hill around the carousel if I wound out 4th gear at 3/4 tank. Last weekend at AMS it happened around the banking below 1/2 tank. Never happened before at AMP but the car is making more grip and pulling more lateral G's with the extra aero now. I could avoid it by short shifting into 5th and not winding out 4th gear above 6k rpms up the hill which killed my top speed and lap times. After topping off the tank with E85 it didn't starve again until 3/4 tank.

Since I added aero and switched to ZII star specs, I also start fuel starving below 3/4 of a tank. I switched back to 93 for the last track day as I was no longer able to complete a full session without starving happening. A buddy owns an evo shop that does a lot of surge tanks and is trying to convince me to put one on the car.

[King Tut]

Originally Posted by gramicci101

A surge tank might fix the starvation problem. I remember the tank pressurization system we used on F-16's, so I figured there must be something similar for cars that also experience high g forces. That led me to surge tanks, which led me to Ian @MAPerformance, who directed me to the above link. I don't know what kind of fuel flow these cars need in a track environment though, and I don't know if they'd work with a flex-fuel system, although E85-specific tanks were listed.

A surge tank is definitely the correct way to fix the problem. I will be adding one in the future. Radium, Full Blown, and SoS all make a kit specific to the S2000. I would be surprised if someone isn't making one for the BRZ/FR-S.

[gramicci101]

Originally Posted by King Tut

A surge tank is definitely the correct way to fix the problem. I will be adding one in the future. Radium, Full Blown, and SoS all make a kit specific to the S2000. I would be surprised if someone isn't making one for the BRZ/FR-S.

I ended up talking to Ian from MAPerformance because he sells them. He strongly recommends Radium tanks. Most of the tanks he sells are designed to mount inside an actual racing fuel cell instead of an OEM tank, but the link he sent me in my previous post goes to Radium's list of universal tanks mounted outside the OEM fuel tank. He recommended using the OEM fuel pump to feed the surge tank, and then use the surge tank's pump to feed the engine. That seems easier than trying to find the one surge tank that would mount inside the OEM fuel tank.

[King Tut]

Originally Posted by gramicci101

I ended up talking to Ian from MAPerformance because he sells them. He strongly recommends Radium tanks. Most of the tanks he sells are designed to mount inside an actual racing fuel cell instead of an OEM tank, but the link he sent me in my previous post goes to Radium's list of universal tanks mounted outside the OEM fuel tank. He recommended using the OEM fuel pump to feed the surge tank, and then use the surge tank's pump to feed the engine. That seems easier than trying to find the one surge tank that would mount inside the OEM fuel tank.

Yep. That is the way the S2000 guys do it.

[gramicci101]

Originally Posted by King Tut

Yep. That is the way the S2000 guys do it.

Not having any experience with modifying fuel systems on cars, it seems like it would be least difficult to mount the thing in the engine bay and access the inbound fuel line there.

[King Tut]

Originally Posted by gramicci101

Not having any experience with modifying fuel systems on cars, it seems like it would be least difficult to mount the thing in the engine bay and access the inbound fuel line there.

Never seen that. Generally it is mounted inside the car or near the fuel tank under the car. For the BRZ, I would ditch the rear cushion and build a nice mount for it in the driver/rear seat area.