Porsche Club Time Trial - What a blast! Poor Porsches
 

First of all, thanks for the advice from everyone about what I should do to prepare my 3rd Gen RX7 for track duty.

Last weekend I went to Pahrump (near Las Vegas) to run at the Spring Mountain race track for a time trial with the Porsche Club of America. If you live anywhere near Vegas and you havn't been to Spring Mountain yet you should go. It's a very technical 2.2 mile track that is designed for training rather than head to head racing. It's a lot of fun, great practice and the owner is super cool and lives at the track.

This was my first track event in my RX7. Everyone, including me was blown away by how fast the RX7 made it around the track. My instructor was amazed when he timed me at a 1:57 around the track. When I pulled off a 1:52.8 second lap during the actual time trial the second day he practically died. He had to check my time several times because he just couldn't believe I was that fast.

I had such a blast and I'm so impressed with what Mazda did with the RX7. Of the sixty or so cars there only six were faster than me. Of the six faster cars all were non street legal porsche race cars that were brought in on trailers and driving by very experienced drivers. Five of the six faster cars where within 2 seconds of my time. One tube frame 1300lb 914-6 based race car did a best time of the day at 1:47.9

The next closests cars to the mazda that were street legal were a 1:54.0 by a very good driver in a nicely prepped Boxter S and a 1:56:00 by a Porsche Turbo S. My instructor got a 1:57 in a highly modified and stripped down 944 Turbo.

I still can't believe my time. That's RX7 is an amazing car.

My suspension was all stock except for Koni shocks set on a middle stiffness setting and Kumo Victoracers. I found the car to be very easy to drive and very predictable. I could drift it out as much as I wanted and it was super catchable. I got sideways twice but easily brough it back straight. Some people have said the RX7 will get away from you easily. I didn't find this to be the case at all.

I did notice that after about 4 laps my engine temp would creep a little bit past the middle reading. I'd take it easy then for half a lap and it would cool right down. I have a ducted Koyo Radiator. Any advice on how to make it cool better? My buddy suggested Water Wetter or a vented hood. Other than that my car ran great.

I was also amazed to get 23MPG driving there on the freeway and then 4 to 5 mpg on the racetrack. I burned 40 gallons of fuel on the racetrack that weekend!

Thanks again for all your help guys!

-John Magnuson
San Diego, CA

RX7s rule!

Now I need to move to Las Vegas so I can drive on some tracks.

so it goes, "the seven can't lose" :)

Re: Porsche Club Time Trial - What a blast! Poor Porsches
 

Here is a thread I started a while ago. Hopefully it will help you address your cooling issues. Our cars just tend to run very hot during lapping days, unless they are really race prepped.

https://www.rx7club.com/forum/showth...for+turbo+cars

i wonder if it would be a good idea to completely flush the coolant system before a track event and run straight distilled water and redline water wetter.

I figure the cost of open lapping is around 110 USD
5 dollars for a bottle of redline water wetter
5 dollars for another bottle of prestone antifreeze after

10 dollars for motor oil change after run

it could be worth the cost since you are paying that much already

Re: Porsche Club Time Trial - What a blast! Poor Porsches
 

R-compounds will definitely mask the snap-oversteer tendencies of the FD. For road racing, I find that offsetting the rebound settings helps to make the car more consistent and allows you add power more aggressively as you track out of corners. I typically run full stiff front and 1/2-1 turn from full soft on the rears.

I have conceded that I need to get a Mazdaspeed GTC nose, if I plan to continue Solo I. It's too much stress to have to constantly be checking coolant temps. Other suggestions for better cooling would be dual oil coolers (if you don't already have them) and running 20W50 oil.

Glad to see you're hooked. Now you've got the bug .... it only gets better. :)

Antifreze also increses the boiling point of the solution so I think you'd be better off with at least SOME of it in your system.

Re: Porsche Club Time Trial - What a blast! Poor Porsches
 

Yeah, I average about 4 mpg on the track. Nothing like being able to burn up so much gas and rubber legally, right? ;)

Thanks for your replies guys.

I guess for my next track event I'll try adding some water wetter and using 15W/50 instead of 10W/30 weight oil. Maybe that will help.

I was also running half a quart low on purpose to make sure I didn't suck oil into my PVC system. This probably didn't help cooling but my car never spilled any oil up the filler cap into the PVC either despite some long hard right hand turns.

I have a feeling a vented hood would help a lot. There just doesn't seem to be any good place for the hot air to exit. But I love the stock look and hate to get some rice rocket looking vented aftermarket hood that probably weighs more and fits like crap. Has anyone put some vents in the stock hood? Can a shop do this?

Thanks,

John Magnuson

I am told by M Avilla, who has extensive track driving experience and has a Mazdaspeed replica hood, that vented hood on an FD does not help much in decreasing engine temps.

BTW, how long was the drive from San Diego to Pahrump?

San Diego to Pahrump is a little over 300 miles. So it takes around 4 hours to drive there... depending on how fast you go.

If you live anywhere near there and havn't been yet you should go.

Pahrump is about 40 miles from Vegas

San Diego to Pahrump is a little over 300 miles. So it takes around 4 hours to drive there... depending on how fast you go.

If you live anywhere near there and havn't been yet you should go.

Pahrump is about 40 miles from Vegas

if anyone wants to host, I have some videos of my FD vs 996s at Laguna Seca last fall

Re: Porsche Club Time Trial - What a blast! Poor Porsches
 

John - like evilrotor said, check out some of the suggestions in the other thread he started. One of the most helpful posts (in that thread I think) was a listing of all the things you can do to lower temps on the track. I just did a whole bunch of them from that list (finished today)... just in time for the weather to cool down around here. Oh well, I'll be ready for next year.

p.s. get a water temp guage ASAP so you can really see what is going on.

Oops, the list wasn't in that thread, it was in this one: https://www.rx7club.com/forum/showth...5&pagenumber=1

Here is the list again, posted by Crispy:
A list of things to do to bring temps down: For general consumption:
1) Bigger radiator
2) 80/20 or 70/30 (minimum) water to coolant mix
3) Bottle of water wetter
4) Twin, or large single, oil coolers (for track use OE units at a minimum)
5) Synthetic engine oil (no debates please...it lowered my engine temps a few degrees where every degree counts)
6) Run lower boost
7) Turn on heater full blast when on the track
8) If have a PFC set fans to come on at lower temp.
9) Drilled thermostat (summer months track only)
10) ***Perfectly sealed radiator*** Ducting on the sides and to the nose, foam in holes around piping pass throughs, etc etc. Hold a bright light behind/under the undertray, in the engine bay near gaps, and look through the nose of the car. See light? Got a hole...plug it
11) Vented hood
12) Throttle body coolant line bypass
13) larger intakes in nose of the car - NTech Sharkmouth mod for stock nose or aftermarket nose piece.
14) Relocate the battery. It acts like a giant heat sink and once heated up it keeps the radiator hot too.
15) Fix anything that's supposed to be working that's not - both fans, any coolant leaks,etc etc.
16) Reinstall plastic undertray

Hmmmm... Thanks for the list.

I've done most of those things. I could still do:

1) Vented Hood - ewww
2) Drilled Thermostat - I dunno about that one
3) Water Wetter - I'm going to try this next time
4) Larger front opening - maybe someday

What about a waterpump underdrive pulley? I notice that M2 sell a set and says it actually increases water flow at high rpm because in stock condition the water pump turns to fast at high rpms to be efficient??

Is this true?

Thanks,

John Magnuson

John,

Congratulations, BTW. Keep up the good work!

I would add 2 things to Crispy's list:

1. Add the 99 front spoiler, dive plane or similar. This effectively splits or seperates air under the car and directs to the rad.

2. Radiator ducting. Fab AL pieces on both sides of the radiator to prevent air from spilling out the sides. Make sure to but it up against both sides of the rad and secure to the AC condensor mounts/belly pan.

Also want to reiterate that sealing the radiator (particularly in conjunction with #2) works very well.

Sealing the rad, the ducts, and the 99 lip netted 10 degreee temp reductions at the track for my car. Hasn't gone over 100 C since.

Gene

I think almost everyone agrees that sealed radiator ducting is the #1 thing to do, so I don't think Crispy's list is in order of priority.
With respect to these two, PFS drilled one single 1/4 inch hole in the lip of my thermostat. They say it should help but not be as radical a change as a t'stat that looks like swiss cheese. And I had my bodyshop open up the front opening in my OEM nose without doing the "shark mod". Looks nice - I'll post some pics soon.
Done that, but think that this just prevents cavitation, doesn't really help you run cooler other than that.

I have not tried it first hand yet but the idea is that with the stock pulley the pump cavitates at high RPM, doesn't push coolant as efficiently and therefore forces temps to rise. I have noticed in my stock pullied car a big difference in coolant temps between shifting at 7500 and shifting at 6500. The pulley makes sense to me as I can make the temp go up and down nearly instantly by changing shift points. I have yet to prove it by switching pulleys though.

The negative of that modification is that your water pump is pumping more slowly during non-track situations....

I think with an FD, there comes a point where you are simply going to run hot no matter what you do (at least during very hot track days). None of those modifications change the fact that the FD engine bay is very tightly packed and the radiator is still undersized.

A single turbo would probably run much, much cooler than the twin furnaces bolted to the side of the engine as well.....

My list. :)
And FWIW no it is not in order of priority...just pretty much everything I did. Gene...good call on the '99 lip spoiler. I agree it will scoop more air into the nose than the R1 lip.
Re: the drilled T-stat. This IMO is a biggie for track use. It's effectiveness is most notable on the street so I know it's working on the track as well. For example in our midatlantic mild mid october ambient temps (60degF) I can barely get my car up to temp on the street...and I'm talking 70-75degC highway cruising.
So it's not advisabel to run one year round or even if it's needed for street use at all.

With respect to the water pump pulley or main underdrive pulley (which I do run also) yes it slows the water pump to prevent cavitation at high rpms...or so the theory goes. The thing to consider though is that for a stock port motor the power curve starts to drop off at around 6500 rpms. So the need to push deep inot the high 7000rpms raneg really isn't necessary. My shift ligth si set for 7200rpms FWIW. So consider that thought.

FD's do run hot but the only time I've had an issue it was in 105deg ambient temps...and then EVERYONE was having cooling issues BMWs, Porsches, tubro...nonturbo...you name it. So I didn't feel bad.
Set up right the FD shouldn't have cooling issues...you just have lots to do to make it so.

And yes I love my vented hood :)
Regards,
Crispy

PS a single turbo will help also but geez why not redisgn the whole car! :D

My plan is to buy an underdrive water pump pulley and use it only for track days. Swapping the pulley (and the belt if need be?) wouldn't take long.

Crispy, if you think the holed thermostat works so well I'll try that too.

So... when the stock temperature gauge starts to rise just a tad above the middle. (Still a little under 2/3rds of the way up) how hot is the car really running? That is about how high my temp would get after 3 to four very hard laps shifting at 7800 rpms.

I'm sure a lot of you have both the stock and an aftermarket gauge. Anyone have an estimate?

-John

P.S. Maybe I shifted too high... but it was fun.

Hey! The results from the Porsche Club Time Trial are in. I ruined their perfect little 10 ten list by polluting it with an "other" type vehicle:

http://www.pcasdr.org/timetrial/2003_10_05_results.html

Yeah for Mazda!

-John Magnuson

I don't know but I have hit 108C engine block temps/230F coolant temps and the stock gauge never moved.....