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Phase 3 - Now for power

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Re: Phase 3 - Now for power

Postby Mark G » Sat Nov 18, 2017 11:52 pm

Does a turbocharged 3.4L engine put you at approx 2,200 lbs for XP?
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Re: Phase 3 - Now for power

Postby grant » Sun Nov 19, 2017 3:18 pm

Mark G wrote:Does a turbocharged 3.4L engine put you at approx 2,200 lbs for XP?

Yes roughly 2200 lbs. if I were to ever run SCCA event would need to ballast . I'm building more of unlimited Hillclimb, TT, PCA Mod car currently. If I were to build ideal xP car I'd likely have to go with newer 2.0 liter turbo 4. But that would be pretty expensive and complex at this point. With TPC turbo sponsorship this bolt on kit makes impressive power and keeps things pretty simple . I don't even need to drop motor to install and it uses my stock ECU, bolts to my existing race headers and intake manifold. Heck it uses my existing Cobb access port to flash new tune for forced induction.
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Re: Phase 3 - Now for power

Postby amrx7 » Tue Nov 21, 2017 1:20 am

I'm amazed you are that light Grant. A 3rd gen RX7 like mine was lighter than a Cayman in stock trim and I worked pretty hard to get it down to low 2000's and that was before I put a cage in. How wide are you in back with big wheels?

-Andy M.
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Re: Phase 3 - Now for power

Postby grant » Tue Nov 21, 2017 7:40 am

amrx7 wrote:I'm amazed you are that light Grant. A 3rd gen RX7 like mine was lighter than a Cayman in stock trim and I worked pretty hard to get it down to low 2000's and that was before I put a cage in. How wide are you in back with big wheels?

-Andy M.

It's funny Mazda and Japanese cars in general dont seem to bolt as much heaviness onto their chassis. Porsche on other hand builds extremely efficient chassis and bolts heaviness on. For example doors. Cayman doors are built like a tank. I haven't weighed my doors but I can barely lift them. Rear hatch is super heavy too. Interior materials are much heavier than Mazda . People don't believe it but Porsche interiors weigh hundreds and hundreds of pounds . My Nisan interior was about half the weight of my caymans. Porsche carpet and insulation is very heavy. Even rubber seals weigh a ton. Then there are Porsche bumper beams. Porsche Accessories like AC weigh more than mazda too. Battery in stock Cayman weighed more than what battery in my Mazda and 370 Z weighed as well. Lots of brackets to pull as well. But believe me you have to be dedicated to pulling every last bit off the car and use lightweight racecomponents to replace OEM suspension etc. even lightweight flywheel sheds tons from dual mass flywheel. Stock exhaust system is a boat anchor on Cayman. The turbo kit doesn't add any weight compared to stock exhaust system. Even OEM induction on Cayman is heavy with huge air box, heavy insulation, heavy rubber seals, etc. The ceramic brakes keep weight down too.

Can't remember what Width with 12 inch and 335 rears. I think I'm still more narrow than say a corvette. Will have to remeasure but car has no problem clearing inside fender wells of my trailer.

When you look at stripped down Cayman chassis you start to see why it's so light as well. These are photos from 1900 lb Hillclimb Cayman build in U.K.

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In comparison the FD chassis looks pretty heavy. Traditional big frame rails out front, big transmission and driveshaft tunnel. And remember inside of that dainty Cayman are two big access openings to motor that are covered with thin aluminum covers. I'm betting lless steel in Cayman chassis body than in FD. Then there is Drive shaft and rear diff, suspension subframe design that I suspect Mazda used. Also wonder if sheet metal in Fd body is as thin as on Cayman? I'm always accidentally denting my car just by leaning on fenders. Crazy thin sheet metal on 987.2. When compare stock to stock dinesions the Cayman is close to same size as FD and it's slightly longer length is more styling than physical steel structure. Lots of air under my bumper covers. In fact other than maintaining shape of the car they don't really cover anything anymore. Bumper beams I removed extended out from chassis into covers. Now there is a bunch of air under covers.


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Last edited by grant on Wed Nov 22, 2017 2:14 am, edited 1 time in total.
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Re: Phase 3 - Now for power

Postby grant » Wed Nov 22, 2017 2:04 am

Andy,

Measured car width at widest point in rear it's approx 72 inches but at cone level proabably closer to 71.
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Re: Phase 3 - Now for power

Postby amrx7 » Wed Nov 22, 2017 11:24 pm

Still surprised it is so light. Newer chassis tend to gain weight, and the RX7 FD chassis had a pretty strong focus on lightweight just about everywhere. I'm also wider at about 74" running 12" wheels with 13" tires. But if you can get sub-2000 with XP prep and be fully ready to run minus driver, that is awesome. Maybe there is a use for our old Boxster after all :-). Granted, I don't even want to touch that car because XP power with a Porsche motor is not cheap by any stretch.

In any case will be good to see you out there next year. I have modest plans for RX7 prep this winter.

-Andy
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Re: Phase 3 - Now for power

Postby grant » Thu Nov 23, 2017 12:45 am

amrx7 wrote:Still surprised it is so light. Newer chassis tend to gain weight, and the RX7 FD chassis had a pretty strong focus on lightweight just about everywhere. I'm also wider at about 74" running 12" wheels with 13" tires. But if you can get sub-2000 with XP prep and be fully ready to run minus driver, that is awesome. Maybe there is a use for our old Boxster after all :-). Granted, I don't even want to touch that car because XP power with a Porsche motor is not cheap by any stretch.

In any case will be good to see you out there next year. I have modest plans for RX7 prep this winter.

-Andy

Think problem is with new TPC turbo my 3.4 liter XP class weight is around 2200 lbs so can't run XP sub 2000 lbs. Even with NA motor I'm at 2080 lb xP class weight. Already hit that weight. If I didn't do hill climbs I'd probably try to just go with NA 3.4 but I get killed by 600 hp cars in my Hillclimb class.

There will be a cheap XP power source soon for 987.2 and newer Boxsters ....and suspect with work 987/986 cars. When 718 2.0 liter turbos lose value and start crashing those motors will likely be cheap. Can likely get close to 500 hp out of that 2.0 T in race trim with tons of boost and e85. Those 4'cylinders are pretty much same motor as current 6 turbos with two cylinders removed. My ECU in 987.2 will run that 2.0 T motor. I don't have time to do a motor conversion this year but that is likely route I will go long term.
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