Talk me out of buying a S8 Rx-7

[mines]

keep the GTR and also buy Rx7!

[justin911]

hey tommyk,

what sorta mods are involved in 'stage 2' upgrade ??

[rx7_ben]

imagine the 13b-rew you could have built for $7.5k! would have been a monster, and on another note just remember the following, reciprocating engines have the following shortcomings:

(1) Because of the reciprocating parts, vibration, noise and power loss become greater as engine revolutions increase

(2) Because of its cranking mechanism, it is heavy and large compared to power output.

(3) Because of its intake and exhaust valve mechanism, it generates mechanical noise and this mechanism requires many parts.

whereas rotary engines suffer from none of these shortcomings, and just remember that rotaries dont have shorter engine lives than others.. I've personally seen them pushing upwards of 450,000km. But like anything if they are thrashed or modified excessively they arent gonna last forever and be an ideal family car are they?

but fundamental design flaws aside, the gtr is a very aesthetically pleasing and well performing car which has proven itself, so it all comes down to your personal preference and what suits your lifestyle best.

[scathing]

just remember the following, reciprocating engines have the following shortcomings:

(1) Because of the reciprocating parts, vibration, noise and power loss become greater as engine revolutions increase

(2) Because of its cranking mechanism, it is heavy and large compared to power output.

(3) Because of its intake and exhaust valve mechanism, it generates mechanical noise and this mechanism requires many parts.

whereas rotary engines suffer from none of these shortcomings, and just remember that rotaries dont have shorter engine lives than others.. I've personally seen them pushing upwards of 450,000km. But like anything if they are thrashed or modified excessively they arent gonna last forever and be an ideal family car are they? 

but fundamental design flaws aside, the gtr is a very aesthetically pleasing and well performing car which has proven itself

1. But, it makes more power at lower RPM. So do you want a street car that makes good power from down low, or something you have to rev the tits off? That said, if you want to talk peak power and a gutless low end, the F20C powering the S2000 makes more power than the 13B Renesis powering the RX-8, with the same redline and far better fuel economy.

2. Tell me, how many all-alloy rotaries are there? None to my knowledge, because they need to be cast iron for strength. The most common motivation for the SR20DET powered RX-7s getting around in Japan is because the all-alloy engine weighs less than the cast iron rotaries they come with, while still making good power.

3. You want to talk noise? Ported rotaries aren't exactly electric motor quiet, and when you're talking about "serious" rotaries (to compare with "serious" piston engines, that make a fair amount of noise) the porting doesn't stay stock for long. Sure it might not be mechanical noise, but unless you're some kind of noise snob that only wants NVH refinement from certain parts of the car its a moot issue...

Speaking of fundamental design flaws, apex seals are inherently weak. A right angled seal can't handle the same load as a circular one. You can replace them with tougher ones, but all you're going is working around the problem in a brute force manner, not fixing a "fundamental design flaw".

Shall we get in to the rotary's total loss lubrication system? Its thirst for petrol that far exceeds its displacement (whether you take swept volume, or equivalent volume per revolution)?

But in terms of percentage per capita, how's the reliability of a rotary compared to a piston engine? Of the rotaries in production, what's the MTF compared to a piston engine?

Most people would agree that any heavily performance-modified and thrashed car will make for a poor family car, regardless of what its powered by. But history has shown that even stock rotary family cars don't cut the mustard either.

No, the rotary doesn't have the shortcomings you mentioned, but its got plenty of others.

[scathing]

To pre-empt the inevitable reply, I realise the rotary has not had the same research and development that piston engines have.

But, for a car I plan on driving most days and out on the track without a professional race team, VC-funded proof of concept, or OEM development, budget I couldn't give a flying fornication what could be. I only care about what is.

A nuclear powered car would be heaps better than a fossil fuel one, in theory. It'll make more power, hardly ever need refuelling (relatively speaking), and have no emissions. But if someone hands me the keys to some swoopy vehicle that glows in the dark, I'll politely decline from behind the first lead shield (or perhaps a stack of rotaries) I can find.

[rx7_ben]

not trying to argue with you scathing but do you have any idea what I meant by mechanical noise? I dont think you did, I meant the sheer ammount of moving parts in the valvetrain. Also there is all alloy rotary engines available, and I severely doubt a sr20 would weigh less that a 13b-rew even though it does have cast iron plates. Also, rotary engines actually make decent power at low rpm but fail to make large ammounts of torque (due to how little is actually moving mass in the engine). Anyway I admire your intelligent and thorough response as you probably know as well as I do some of the crap that comes out of people's mouths about rotary engines haha

[Tommyk]

This thread is still going .... interesting

Anyway, I might just let you know ive gone the GTR way with:

New turbos

New cams

new injectors

new afm's

new clutch

and a sump baffle kit

That gear should provide for some decent power.

I'm now afraid i will have to upgrade the rubber and the suspension

[Mr R32 M-Spec]

Interesting, do you have much in teh way of Suspension/Braking mods so far?

mark

[Tommyk]

Ummm, no not really

Please dont remind me, because then I'll probably look into upgrading my rotors + calipers and suspension

[scathing]

but do you have any idea what I meant by mechanical noise? I dont think you did, I meant the sheer ammount of moving parts in the valvetrain.

Yeah, there's a lot more complexity in the breathing parts of a piston engine. It also means that there's more capability of failure in them. I was considering more audible noise from mechanical parts, to be honest.

I wouldn't mind getting a fair comparison with the weights of a 13B-REW out of a Series 8 RX-7, and an SR20DET out of an equivalent year S14/S15. Its hard because some people do and don't include certain ancillaries in the mass.

If someone could pull the engine out (so drop the engine mounts, disconnect it from the driveline while leaving the flywheel attached, unplug the battery and fluid resovoirs, but include radiator, intercooler, all piping etc and have them both with a full sump) it would be quite interesting. The 13B will still be shorter, which improves weight distribution.

I suppose I used low-end power in the wrong context there. I was more after oomph, and an ability to accelerate from all across the rev range (so I meant torque). My VQ35DE makes reasonable torque from 2000RPM and only tapers off at 6000RPM because of the quiet factory exhaust. I also make more power than a Renesis engine with just over 2/3 of the RPM, while using less fuel.

[leb]

Get an Rx7- goes wayyyy harder after some slight modifications