The Infiniti M45 is a 4000# car w/335 shaft hp & a 5-speed automatic. It runs 13.7 1/4s.

The RX8 weighs 3000# and has a 6-speed manual with good ratios. I would think that with 300 shaft hp (which can be had from a well-tuned Greddy setup with a couple of extra #s of boost), this car should be running low 13s with this power/weight ratio.

Is the problem traction? Won't the tires hook up? Or am I missing something?

 

its possible and has happened before. as a matter fact, if i remember correctly, i think someone here is claiming high 12's

denward

 

Well, a lot of it is torque curve. You're figuring in Horsepower, but not Torque, which is the most important factor if you're looking at just 1/4-mile times.

An M45 has 333lb/ft of torque. An RX-8 has 150 lb/ft stock and some 200 lb/ft Turbo'd. That's a rather substantial difference.

That said, yes, a well-tuned GReddy setup could presumably hit low 13s. You should hit mid to high 13s with 240hp which is about average for a GReddy, so if you could grab another 20hp and some more torque you might could break into the low 13s.

EDIT: I'm also curious where you're getting your 13.7 1/4-mile times for the M45. All the published times I'm finding are quite a bit higher than that, ranging from 14.3 to 14.7.

 

Whoops! Actually Road & Track quoted 13.8 (the BMW 545i was 13.7). http://www.roadandtrack.com/article....&page_number=4

Yes, there's a big torque difference, but also a 1000# weight difference and 5-speed slushbox vs. 6-speed manual.

Anyway, I am going to feel mighty silly dropping this much coin on a mod if it doesn't make my car faster than an overweight, overpriced Nissan, er, Infiniti.

 

Well, when you start talking about that much power, Manual vs Automatic makes little difference. Often at such high torque numbers an Automatic can actually post better times -- look at the '05 GTO for an example of that. Also, the Infiniti can probably make the 1/4-mile run with 1 less shift than a turbo'd RX-8 will require (guessing the RX-8 will have to go to 4th, not sure on that), which will tack on an extra couple tenths or so right there.

And, if indeed that time is correct, and I still find it a bit hard to believe, I wouldn't exactly feel "bad" about not beating it. That's on par with a '05 Mustang GT -- which is one reason why I find that number hard to believe.

 

Yes this is true with the new GTO's, but we are talking 350-400 stock HP and Torque. The reason the autos are faster is because of traction and if you try and clutch drop a manual you will spin out for days or the wheels will smack the car body. I doubt that this will happen with a 200-225 lb-ft RX-8.

Also, automatics are only faster than manuals because of the amount of gears. They are not shifting anywhere near as fast (except SMG's) they just simply don't shift as much.

 

gearing plays a part too.... it seems the rx8 would benefit from lower gearing

 

Yes, this I know. I'm the one that told you that in your other thread, as I've driven both ATX and MTX '05 GTOs. But my comment was in reference to the Infiniti with its' 340lb/ft of torque, not the RX-8.

 

Ok let me get my question out then.

FD Rx7 stock has not much more hp than an rx7 and an FD with 240hp at the wheels probably runs a low 13. So why can't an 8?
________
RachelTS

 

Well--I'm not sure about the specifics but the RX7 was slightly lighter weight, the rev band was different, and the tranny was a 5speed. The automatic FDs are slightly faster than the 6spd RX8s and they have the predecessor 4spd auto of the a/t RX8.

 

Beacuse, depending on equipment, the RX-8 has anywhere from 200 to 400lbs on the RX-7.

 

I'm pretty sure it's more like 200 or less unless your carrying a lot of extras. Rx7 2800 lb correct?
________
Hitomii live

 

The specs I found on the RX-7 had it ranging from 2750 to 2900. The RX-8 weighs anywhere from 2950 to 3100.

 

Speaking of weight, is the RX-8 more affected by additional weight than most cars are? I noticed that when a friend and I are in the car (I'd say...combined weight of 330)...the performance seems diminished enough for me to actually notice ...compared to when it's just me in the cabin. Is it my imagination or does an additional 160 - 170 pounds make a big difference here? I've also got the spare tire in the back and was planning on putting in another system later on..

 

I don't know if I'd go so far as to say it's more affected than "most cars", but definitely more than a lot of them. With such little torque -- the RX-8 has less torque than even many compact cars -- you definitely notice the extra weight off the line, even if it's just an extra 100lbs or so.

 

It's not your imagination. Whenever I have a passenger, I can definately feel a difference in performance.

 

The problem is not the 8 can't run 13's, its that very few people are bringing the 8's to the track to even try. Only Adrian has and did a very respectable 14.0 considering the issues with holding boost he was having then. Who knows what the circumstances were in the speed magazine. We need to motivate more people, including myself to go to the track. Maybe we should organize a track days at a 1/4 mile strip in an area where multiple trbd 8's live. Perhaps in northern Va, I know of at least 4 who live here.

In my opinion I am very confident the 8 will do high 13's no problem, and with a good driver mid 13's. I don't understand how this conversation is going on like this. Everyone is talking like it has been shown that a turbo'd 8 will not go 13's, no one, with a properly running kit has tried!! At least not that I know of.

 

The people that do try usually aren't that hard on their cars for fear of transmission failure. Ferdinand Porsche said it best when he described the best race car. It should be just reliable enough to cross the finish line in first place and then immediately fall apart. That's how you have to drive your car to see it's "true" potential. Don't worry about reliability. Just go for it. Not many are willing to do this.

 

I did a 14.7 @ 94 N/A, stock motor, no ECU/Piggyback, just my own exhaust.

Bring on forced induction. :D

Cheers,
Hymee.

 

One time I did a high 17 in a "chipped up and exhuasted" LS1. But I did something wrong that time. It was a mid-13 second car. Then again, I beat a 12 second car when he did something wrong. :D

We are getting there, it is just a matter of evolution.

BTW, Phil had a N/A rensisis do a 13.0, not in an RX-8 though, and with a full Motec ECU.

Cheers,
Hymee.

 

Are you sure of that? I thought it was Colin Chapman. Or were there similar statments?

And what the hell happened to the E mail notices?

 

RG next time I'm in Houston we may have to go to Baytown. Still Stock though

 

I might be in Austin this weekend.

 

Truthfully I'm from Houston and have only lived in Austin for 3 yrs. and as far as I know the closest track is Seguin and i think it may be 1/8 mile.

 

Actually Temple Academy Dragway is about 50miles from Austin. It's a 1/8th mile but they do some 1/4mile racing also but it's short.
Seguin (san antonio raceway) is 75miles away and it's much better and a "real" 1/4mile track.