markd

I know I'm probably going to get flamed for even bringing this up, but this question regards the AUTO tranny 8's performance at high speeds. I was on the interstate last night (little to no traffic, to debunk safety concerns) testing the limits of my A/T 8 and was very disappointed to see VERY sloooow acceleration once I hit 100mph. To get from 105mph to 115mph took FOREVER, and I was flooring the pedal (all the while, I was getting smoked by an A4). The only jolt of acceleration I felt was when the car shifted itself from 4th to 3rd at 89mph. Everything on my car is stock, by the way. No modifications.

I guess my questions are: 1) Is this the way the engine is supposed to perform (I thought the Renesis thrived at high rpms)? Anyone else had similar experiences, perhaps while they were out at the track? 2) Does the manual tranny perform similarly at these speeds?

At the rate at which I was accelerating, I doubt I could ever have gotten to the 150mph limiter--not that I ever would have, but just for the sake of putting it into perspective... I remember one in-depth thread regarding the A/T's performance limitations but wasn't sure if this scenario applied.

StewC625

One simple explanation ... 198 horsepower there. I would guess that the auto trans's top end is way less than the 145 that the mannytranny is capable of. Perhaps 120?

To give you an idea - I accelerated my manny-tranny -8 to 120 mph from 65 in about 20 seconds - redline in 3rd, shift at about 80 mph, and then a long-hard pull to just sort of 120 in 4th, a shift and then still strong pulling in 5th. I ran out of room at 120 and had to shut it down. Nothing slow about it.

Feras

iTrader: (1)

i find if im cruising around at 90 or so on the highway, i easily find myself creeping up in to the 100s...and when i try to go fast it doesnt take long at all to get into the 130s, it slows down there for me though.

G8rboy

That doesn't sound normal to me... not that I have an auto, but at the higher RPM's you should be able to accerlerate nearly as quickly as the MT's (until you hit the lower redline of course). A 120hp car of our weight should be able to easily 125mph. I would bring this up to the dealer as a possible coil or plug problem.

What RPM's were you at when it was bogging?

therm8

seems a little odd, I don't have this problem running 3rd all the way to redline (approximately 120-124 mph, don't remember exactly). It's not blazing fast obviously, but it is a steady pull. Mines stock, except for a catback. Perhaps your air filter needs changed, but then i guess you'd notice breathing problems at any speed at high revs. Hmm, dunno...

310Guy

Yes, you will get flamed. I don't care if no one else is around, you're stupid to be driving that fast on a public road. When you crash, just make sure you don't hit anyone else because of your stupidity...

Vaillant

Is it a gear ratio thing? I thought top gear on the auto was pretty tall (taller than sixth on the manual) which would mean acceleration would definitely suffer. Gas mileage, on the other hand, would be improved (neglecting losses through the slushbox).

On fact, isn't the fastest gear on the manual fifth gear?

~ Matt

markd

I'm not sure what RPM I was at. I do know that I was in 4th (highest gear on the auto), so it was probably around 4000-4500rpms?

I planned on taking it to the dealer to look at it but wasn't sure if it was a problem until now. Not sure how to explain it to them--hypothetically, wouldn't I experience simiar problems coming out of the other gears if it was a coil or plug problem?


120 mph in 3rd? Do you have an auto or manual???

mikeb

I agree
100 plus is way to fast on the highway

unless you are trying to impress a girl J/K

Feras

iTrader: (1)

yeah i find most girls are afraid of speed, big turnoff for a lot of them

markd

I won't argue over whether or not I was right in what I was doing. For all intents and purposes, going over 100mph is a bit excessive (although, at least here in Atlanta, it's not that rare). However, I'm obviously not here to brag about how fast I was going but, rather, to determine if I have an engine problem of which I wasn't aware and to resolve this issue if I can. That's all :o

mikeb

Dont drive 100 and you wont have that problem

just kidding again

spork

the biggest thing about driving over 100 is i think it's considered a felony if you're caught. it might be an urban legend that's been passed around but as far as i know it's a felony. so i'm not too sure how well the dealership is going to take that problem because how are they gonna test it (unless it's on a track or something).

G8rboy

It really depends, but you have to consider the load on the engine as well. I had a failing coil pack on my Miata, and it wasn't noticeable when driving gently around town, but when putting a large load (pulling hard at high speed) it became very noticeable... it was arcing outside of the coil more than into the wire, and it felt like I was suddenly on 3 cylinders (which in effect I was).

Gord96BRG

1) The Renesis does thrive at high rpms - but those high rpms are 6500 - 9000, or more specifically, in the high-power version used with the 6 spd manual trans.

2) I suppose if you tried to accelerate from 90 mph in 6th gear, it wouldn't be quick - but in 4th and 5th gear, the manual trans RX-8 pulls much stronger than that.

There's been some previous discussions of the AT's top speed - including, I recall, suggestions that the AT RX-8 had a limiter at around 125 or 130 mph. Perhaps a search would turn up the prior threads?

Regards,
Gordon

G8rboy

Well, laws in Cali never fail to amaze me, but I don't think it's a felony anywhere else. Let's just say I've never been taken to jail... just a ticket.

therm8

auto, and I just noticed your complaint was with 4th gear accel. 4th gear ratio is 0.69, 3rd is 1.00 so there would be a noticeable decrease in acceleration upon shifting to 4th

not anywhere I've ever lived. doubling the speed limit however, is more likely to be. Depends where you live I guess. The smallest penalty for doubling the limit that I 've seen was suspended license for 6 months and up to 30 days lock-up(usually waived and a fine instituted)

here's something that was posted a while ago, regarding gear ratios

quack_p

therm8, sorry if this is a dumb question, but what are the numbers under RPM? Are those speed numbers? So a car in first gear at 3,000 RPM should be at 14 mph?

therm8

correct, these calculations do not account for drag or road friction, so the faster you go the more error there will be

brothervoodoo

I found a similar chart at the UK site and tried to interpolate for our cars... Here's the thread:

https://www.rx8club.com/series-i-tech-garage-22/rpm-versus-mph-25420/

This did not go over well with the forum members and soon got shot down..

spork

Hmmmm... I can't really find any evidence that it's true, but I know I've been told this from many different sources. And looking it up quickly on google gives me various other people saying it's a felony in California but not backing it up or saying if it's true elsewhere too. A coworker of mine is adamant that is a felony here and from the web I see it is a 2 point violation in California on par with

Evading peace officer/reckless driving
Driving while suspended/revoked
Hit and run/injury/property damage
Driving wrong side/divided highway
Reckless driving
Reckless driving/causing bodily injury
Speed contest /exhibition of speed
Minor driving with BAC of 0.05% or more
DUI/alcoholic beverage or drugs
DUI/causing bodily injury or death
Explosives transportation

so it's pretty serious in Cali. Not sure about elsewhere.

youpey

how do you tell the dealership

ya, when driving over 100 the car seems to accelerate very slowly...fix it!!

G8rboy

They shouldn't put a speedo in that can go over 100 if they didn't expect people to try it out :D

czr

iTrader: (3)

Cool. you got any pics?

G8rboy

Um... sure you do. Which RX7 came with a 20b motor? And a twin turbo? And you managed to fit that into the RX-8?

Unless you bought that Acosta racing RX8, then I must call bullshit