Kale

just curious :confused:

8388

I've taken mine all the way to redline in 5th, then gone to 6th and was still pulling although very slowly, couldn't tell you what rpm that was cause the damn thing was really moving.

SNKSKNR

:bs

8388

I'm not the only one that has experienced this, check into this.

SNKSKNR, your just jealous.

Ultra Slow

With stock gears (3.45's) the RPM is 7200-7300 and the speed is 189 on the spedo. I have done this in over a dozen different ZR1s from stock to moded. They all will redline 5th gear and the spedo is 189 everytime. Some just get there faster than others depending on what is done to it. ZR1's with exhaust and basic bolt ons will pull 6th a bit on a long road. The fastest I have gone in my ZR is 191 on its spedo. Probably somewhere about 185-190 in reality being conservative for error. The rpm drops back down to the 5000 range in 6th at 190. With 4.09's and some bolt ons the 6th gear can be pulled a bit higher, but will it go faster than 190, I cant say yet.

Kale

hhmn thanks

8388

Don't you just love it when a couple of guys that never owned a ZR-1 and would never take it ***** out even if they had one call B.S. on somthing you've done many times.


SNKSKNR you should tell these boys how fast we've gone, then they can take their calculators out and do the math !

MWR

A gear ratio calculator makes this pretty easy, and makes redline in 5th an iffy proposition (at least on level ground).

On a stock vehicle, 180 MPH should be attainable and that would be about 6000 RPM in 5th. My mostly stock vehicle at 160 (GPS) turns about 5300 RPM in 5th. It would have easily gone faster, but I did not have the safety clearance (equip) to determine how much.

Also, a stock ZR-1, with stock gears, will almost assuredly run faster in 5th than in 6th. Even with a rear axle ratio change, the stock 3.45's are about the best ticket for the highest top end (assuming a mostly stock engine).

7000 RPM in 5th gear, in a ZR-1 with stock gears and tires, would be 210 MPH. I'd have to cough a bit on that one, unless there was serious HP under the hood (say, 600).

Note that the ZR-1's I've seen read a bit low on the speedo... a couple percent (which would be 3 MPH at 150). My personal observation, on my car, is that the stock tach reads 50-100 RPM low in the upper ranges. ECM fuel cutoff is supposed to be at 7200 RPM (factory redline is at 7000).

Calculations are based on a 0.74 transmission ratio in 5th, a 3.45 rear axle ratio, and 25.7" tire height (315x35x17 plus 0.1" for growth).

Rgds,
Mark
'92 ZR-1 #032
Y2K SSCC & PE II participant


[Modified by MWR, 4:55 PM 9/29/2001]

Ultra Slow

Yes, the math I get says a bit over 210MPH at 7300 RPM. Everyone will agree that the ZR1 is one of the most underrated cars around, but I doubt that 200 is abtainable in any ZR1 with mild mods. There is probably an error in the formula on the OD factor. I figured a 2.56 final drive in 5th with 3.45's and the ZF .75 od and if you use the formula;

7300x25
----------- = 210 MPH ........ Right..... I say too.
2.56x335

The fact is that every ZR1 has a rev limiter around 73-7400 RPMS unless you change the prom to one that raises it. EVERY zr1 from 90-95 from stock to bolt ons shuts off right at 189MPH on the ZR1 speedo as the rev limit is hit in 5th gear. Trust me on this as I have done it tons of times. I have even pulled 6th a very little bit on cars with exhaust and basic stuff to about 191MPH. What it is actually doing I guess we will have to GPS it with a fast updating GPS for an acurate reading. The math says its going tons faster, the car says 189-190, my logic says about 185.

MWR

Ultra, we probably agree except for the terminology. If the car is 'shutting down' at 189 MPH in 5th gear, then it's hitting some type of MPH limit, not a rev limit (as we've examined, the 7200 RPM rev limit in 5th would be way over 200 MPH.

MPH limits are far from uncommon, altho I'm surprised one is implemented on a Corvette. Or perhaps the speedo simply does not register anything over 189. Hmmm... may be time for a 3AM run :D

My personal experience, and that I've gleaned from other ORR drivers, is that the car is going a few MPH _faster_ than the speedo says. A basic GPS unit will confirm this (I have a $200 Garmin unit from Wal-Mart, works like a champ at 170 ;) )

8388

Here's a formula that I have used for many years, and its even in the back of my Crane Cams book.

RPM= MPH x gear ratio x 336 divided by tire diameter

Ultra Slow

Yes the GPS is a great deal, but remember it only updates every so often and you could have actually gone faster than indicated between its update intervals. There is NO speed limiter in the ZR1, only an engine rev limiter. We can debate all day long on the math and the numbers do not lie as I have done them myself many times and am well aware of the formulas and they dont lie. I cant understand it myself and would just pass it off to a wierd car, but I have owned, worked on, bought and sold tons of ZR1s. Every darn one that I have topped out does exactly the same thing and EVERY zr1 will hit this exact speed if you give it enough road. Modified ones get there much quicker but still have to go into 6th at 189. The ONLY logical explination to this might be that the specs on the ZF 5th gear is not actually .75, possibly closer to .79. The tires are a given 25" on the average ZR1, the gears are a factual 3.45, the tachs may be off a couple 100 on various cars, but the ECM still shuts it off at roughly 7300. Doubters just try it in 2ng gear, dont let off untill it hits it, others that have the nerve, just run it out in 5th. If you have an aftermarket prom as I do in my toy, this may be eliminated so be carefull. The only variable that could make all this debating logical the OD ratio.... I'll let someone else do the homework on this to see if the factory is quoting an exact ratio at .75 or just somewhere close.

MWR

Ultra, to put a post mortem to this thread, nobody is redlining a ZR-1 in 5th gear. The numbers simplly do not support it. Nor is anyone going faster in 6th than in 5th. It may be possible in a few exotic incarnations, but that's about it.

In other words, you can pass _any_ C5, but don't expect Michael Schumacher to move over....


[Modified by MWR, 12:07 AM 9/30/2001]

drive it

[QUOTE There is NO speed limiter in the ZR1, only an engine rev limiter. Ultra slow-sorry to quible the small stuff but.... I just had to check tunercats AF and AFA tdf,s which are the definition files for the earlier ZR-1s. It's the same as 6E's 8d's etc. when it comes to a "speed limiter." Look under ECM constants-then find "fuel cutoff speed". Yes its there, however in looking at a stock bin for a 91 ZR-1 its factory set at 255mph. :D

8388

O.k this has been bugging me all day, and I just got back from running the Z earlier today I looked up the 5th gear overdrive ratio and according to the manual and its .75 not .74 , I measured the rear tire and as best that I can see its 25" no more no less because I know that the formula does not lie, and granted my tach may be off aswell my speedometer. this is what I saw I ran up the gears and took 5th to about 7000 - 7100 rpm the mph was showing 190, I wanted to try 6th but but I kept getting too close to traffic so I had to backed off both attempts , plus I didn't want to push my luck.
Now according to the formula 190 x 2.59 x 336 divided by 25 = 6613.824 rpm now maybe my tach is off by 400 or so rpm's or my mph is off or both I really don't know, but I do know this in a lower gear once the tach passes 7200 rpm the fuel is defintely cut off, this car has a K&N air filter with the filter cover cut out and 3" exhaust by desert development with a cross over and some good flowing mufflers, and thats about it. What it did tonight is not much different than what its done many times before, also this is not the fastest car I own and I have tried to be very honest about the way it runs I never felt I had to B.S about its performance especially in a forum full of ZR1's almost every time I've or we've done this we've had someone eles in the car that has seen the car do it, and to be perfectly frank I always thought that ZR1's with about the same mods performed about the same as mine does.
BTW the weather was perfect tonight nice and cool .

Well its late so I'm calling it a night.

LT1pwrd'94

8388,
Did you ever have problems with your ZR-1? or do you just not drive it much? Last time we came by, SNK was sayin something about it, but im not sure what. Just checkin. :seeya


[Modified by LT1pwrd'94, 11:56 PM 9/30/2001]

LT1pwrd'94

8388,
How is your '88(35th anniversary) runnin?? Is it still at Matt's house? I havent heard it mentioned lately, just curious.:confused: You leavin your ZR-1 the way it is or are ya gonna mod it more?? :chevy :seeya

8388

On the ZR-1, 2nd gear syncro is not doing too well, as far as more mods, not likely, as you know I got plenty more to keep me busy. The 35th is still at Matts, and will probably remain there till I get my new garage , don't take it out much since it sits at the back of the line plus its kinda loud ( not as loud as SNK) but enough to bug the neighbors especially late at night when every one gets the urge.

9TZR1

Man, you guys doing 190 have great big b****. I was nervous doing 180 in a winston cup car. Guess I'm getting old I can't think of any roads here in Virginia that would lend it self to those speeds. Be careful!!

8388

Well we had a perfect place, I don't want to give the name out but those who came out know where I'm talking about its 3 to 4 lanes and and untill it was completed we had about 15 miles of no traffic especially after midnight, infact even the local P.D. used to park and watch us go, but now that it is completed it has more traffic not so much after 2a.m. but enough where I couldn't try for 6th this last Saturday.

P.S. on the speed, when running a good competitor, one that stays beside you all the way up, what ever speed we go does'nt feel fast enough, Its only when doing it alone that you feel content and understand how fast your really going.