SR20 Time Attack MX5

Branno · Postby **Branno** » Tue Apr 22, 2014 2:43 pm

Really cool car!
Ive recently converted my NA drift car to SR20DET last October using the THAI-PHOON kit.

My question to you is, How did you go about installing the FC diff?

Series 4/5 NA diff?
Can you use the original mx5 pumpkin and do you have to change half shafts?
Im currently using a NA8 Torsen diff.

PapaSmurf · Postby **PapaSmurf** » Tue Apr 22, 2014 3:11 pm

Thanks Branno,

I bet you notice the difference with the SR20? I'm afraid I can't help you with the diff answer at the moment as the car already came with the FC RX7 diff (series 4) , RB25 gearbox and custom drive shaft installed. When it's next on the hoist I'll get my mechanic to have a look and see what he says. Might be about a month away.

Will get back to you.

Dean

PapaSmurf · Postby **PapaSmurf** » Mon Oct 06, 2014 1:30 pm

Hi Guys,

It's been a while so I thought I'd give you an update on the SR20 MX5.

Am heading to world time attack in 2 weeks time for a run around Eastern Creek in Open Class. Will only be running medium compounds and it's my first time around the circuit so am not expecting to be super quick. Will only be running 20psi as well... unlike some friends who are running 30psi+ and 450wkw on softs.

The car has been progressing well, but the extra power is causing some headaches in certain areas, which we are slowly ironing out.

Main updates are:

- The 20psi boost is producing about ~420rwhp at 7,500rpm limit on e85.
- Rear tyres are now 295 x 18's. (Grip is pretty good considering the power).
- New front splitter arms as the downforce was ripping the front off the car.
- Plastic screen on roll cage roof to get cleaner air to rear wing.
- Some pipework changes.
- Some suspension changes.
- New alcantara steering wheel.

Things to do:

- Need more front downforce as there is some high speed understeer.
- Need completely new brake system as the existing Wilwoods are a little old, not that great, and DBA no longer make RX8 2 piece rotors. (My old Honda S2000 also braked better than my current set-up).
- Need bigger front hubs (The current ones are too small and the bearings are packing it in fairly quickly).
- Still haven't put the carbon doors on.
- Other bits and pieces.

Track Times:
Unfortunately, I haven't had much track time on the 20psi and 295 rear tyres, but did manage to post a flat 54.00 secs on the QR sprint circuit and a flat 56.00 secs at Lakeside on some old tyres, so it should drop at least 0.5 sec with some better rubber and more work around car balance.

Have attached a few more pics.

zero00 · Postby **zero00** » Mon Oct 06, 2014 2:42 pm

Have enjoyed watching your car over the past few years at Lakeside Dean - have a great time at WTA! :wink:

Is it still road registered?

PapaSmurf · Postby **PapaSmurf** » Mon Oct 06, 2014 2:59 pm

Thanks Speedracer. Yeah, still road registered, but I'd have to take all the aero off and put the narrower wheels back on.

Dan · Postby **Dan** » Mon Oct 06, 2014 3:14 pm

PapaSmurf wrote:Track Times:
Unfortunately, I haven't had much track time on the 20psi and 295 rear tyres, but did manage to post a flat 54.00 secs on the QR sprint circuit and a flat 56.00 secs at Lakeside on some old tyres, so it should drop at least 0.5 sec with some better rubber and more work
around car balance.

Damn, this car looks great and 56 seconds around Lakeside is moving!

Will keep an eye out for this at WTAC

PapaSmurf · Postby **PapaSmurf** » Mon Oct 06, 2014 4:24 pm

Thanks Fast Driver. Yeah, it is moving... and quite scary at Lakeside. It's taking the kink flat at 220-225kph, but is very light, floaty and understeery at the front. Not to mention having to feather the throttle out of every corner. A pro would easily be a second quicker than me.

16bit · Postby **16bit** » Mon Oct 06, 2014 4:41 pm

have you got a front diffuser or just flat floor?

also have you considered putting up a fence to block the sides of the front tyres poking out?

such a mean car, good luck at wtac!

Magpie · Postby **Magpie** » Mon Oct 06, 2014 4:51 pm

PapaSmurf it is always good to see you and your car at Time Attacks.

Good luck at WTAC.

Dweezle · Postby **Dweezle** » Mon Oct 06, 2014 6:04 pm

I can not wait to see how you go at WTAC.

I have been looking forward to seeing this in the flesh.

PapaSmurf · Postby **PapaSmurf** » Mon Oct 06, 2014 9:50 pm

Thanks Guys, I won't be that competitive at WTAC as I haven't dríven Eastern Creek before and will only be running 20psi on medium compounds. Most teams will be running 32psi+ with soft tyres and pro race car drivers, so I'll be well off the pace. Mainly going to be part of the atmosphere and to get some laps in.

With regard to 16bits question, the car can't run a flat floor as per Open Class rules. The splitter and diffuser can only be a certain length and must not pass the axle/suspension mid point.

16bit · Postby **16bit** » Mon Oct 06, 2014 10:35 pm

balls!

must be tricky to get that extra bit of front downforce.

might need to spend a couple of grand to get mr brilliant to give it a once over and put some suggestions in!