29 replies to this topic

[BreathlessPerformance]

Through all our dyno tests of over 30 Miata's and over 500 1.6 and 1.8 dyno runs we allways get to 115 mph in 4 gear before bumping the rev limit at about 7100rpm. Dyno tests show the 1.6 making max power about 7000 rpm and actually making a few more HP over the 1.8 above 6500 rpm. All the Miata cars running either at Sebring, Road Atlanta or Homestead with banking reach over 111 mph very easy. Thats even in a 200,000 mile stock engine. In Sebring we just hit 5th gear at the end which is again over 115mph. We can bring a radar gun to Sebring to test the speeds just before the inside wall at full speed coming to turn 17.

[Caveman-kwebb99]

WOW, you just cant keep quiet can you? I know you think you are giving everyone a clinic on here but give it a rest already... I know its grease, and setup, and draft, and now some mph test. I can tell you nobody goes 115 at Mid Ohio or anywhere else in the world in a Spec Miata in 4th gear. After racing 7-8 of the top SM guys in the entire country I got to 115 on the back straight at ATL once it sure as hell wasnt in 4th gear. I would defy to to show me one top SM racer that goes that fast in 4th gear. Get a life!!!!!!!!

[Jim Drago]

Ernie
I'm too lazy to do the math, but the dyno data( Dynojet) I have on a 1.6 is 109mph, it is 109 mph in 4th at red line of 7100. All the 99's redline out at 7000 and about 107 mph. The max MPH has nothing to do with power, just gear, rpm and dyno speed sensor I guess. I am sure some engineer will do the math by the morning
Jim

[BreathlessPerformance]

Thats weird on our dyno we have a shut down at 115 and both the 1.6 and the 1.8 hit just over that. I will check on the race pack to check GPS speed. We run a Mustang dyno and just had Selins car on it and the same 115MPH just before the rev limit. Could the mustang dyno be that far off? I will check with Mustang tomorrow. Was the test you did on a dynojet? We have not really looked at my speedo since it I know it is off as well as the tach. I have seen 120+ on my Spec Miata on the back straight of Sebring and thought it was really closer to 111MPH. Next week I will use the GPS to get the right readings

[BreathlessPerformance]

We might be halfway right, I just saw a video on YouTube showing the RacePack GPS data showing 4th gear at the end of Atlanta straight around 7100rpm 111.1 MPH

The Mustang dyno might be off 3 or 4 mph which you can only check by GPS on the road.

[Charlie Hayes]

I have loads of 107-108mph 4th gear gps data in a 1.6. 82-83mph in 3rd.

[BreathlessPerformance]

Thanks, are they just before the rev limit7000 or 7150?

[Charlie Hayes]

What ever the stock untouched ecu puts out. Do not log rpm yet and just a stock cluster gauge usually not staring at it at 107-108mph just wishing I had time to shift after 3 or 4 bumps of the limiter

[BreathlessPerformance]

Thanks, I know my stock gauges are far off. Stock RPM gauge is slow by 400 and mph is way off. i will check it with a GPS next weekend to make sure. I had to install aftermarket RPM gauges in all our customers cars including mine to get a more accurate number. I know for Sebring I shift to 5th at the 400 to 500 ft mark and continue down to the 100 before tapping the brakes.

[Keith Novak]

It's actually probably pretty close. I show a hair under 111 at 6950 in my 1.8. If I could go to 7150 that would put it about 114mph.

[Alex Bolanos]

Through all our dyno tests of over 30 Miata's and over 500 1.6 and 1.8 dyno runs we allways get to 115 mph in 4 gear before bumping the rev limit at about 7100rpm.

Change the crystal in your computer back to the stock one or swap an unmolested computer back in.

Dyno tests show the 1.6 making max power about 7000 rpm and actually making a few more HP over the 1.8 above 6500 rpm.

There is a device that the 1.8 cars use called a restrictor plate which reduces power at the top significantly over an unrestricted engine such as the 1.6L in the 90-93 cars. If the 1.6L that you are dyno "testing" makes more horsepower than any 94-2005 1.8L Spec Miata then you've gone beyond the bounds of the rulebook and will probably continue to post questionable videos on the internet. Drago can correct me here but the intent of the current rules is that the 1.6L cars make LESS horsepower than the 1.8L cars, hence the weight penalty on 94-2005.

All the Miata cars running either at Sebring, Road Atlanta or Homestead with banking reach over 111 mph very easy. Thats even in a 200,000 mile stock engine.

In 5th gear, yes. Engine mileage has absolutely nothing to do with the ability to hit a certain mph in a certain gear.

[pat slattery]

Alex, he was only stating the 1.6 vs 1.8 made a little more above 6500. Other than that I agree with what your stating.

[Ron Alan]

For us...95 car, 6900 rev limiter, 107-8mph in 4th. This is based on the Rumblestrip GPS speed and tach.

For you engineer types, we know 4/32 tires are slower because of weight(rotational mass), but given this is the one variable that can change in the "speed equation"...just curious if it is measurable? Basically if a 3/32 difference in the radius(4/32 vs 1/32) would show up as a difference in speed(on GPS) given all other variables constant...7000 rpm, 4th gear, 4.3 diff.

Jims comment just got me thinking math...

[Charlie Hayes]

Ron a couple 32nds will not be worth anything. The most you will see between full 8/32 and a cased tire will be a mph. Then it comes down to being consistent enough to even get to the point of discrepancy. That's not where the problem is.

[Todd Green]

WOW, you just cant keep quiet can you?

+1 See pic below. Note the RPM and speed. Also note the RPM's drop as it hit the rev limiter where I have the cursor. This is a 1.6 on BFG R1's.

[BreathlessPerformance]

It's actually probably pretty close. I show a hair under 111 at 6950 in my 1.8. If I could go to 7150 that would put it about 114mph.

So it could be 111mph in a 1.6 at 7150rpm right? Hey Alex the Mustang dyno reads all the Miata cars at over 115 mph in 4th. Nothing to do with a computer chip. Even Selins dyno mph in 4th was over 115MPH so I guess he has a chip in his car? It could be the Mustang dyno is off a few MPH, that was the question. None of the cars we ran on our dyno have a chip in them, to me the dyno is off 3-4 mph. Anyone is welcome for free ( as always ) for spec Miata to come test their car on our dyno.

[LarryKing]

WOW, you just cant keep quiet can you

Not gettin all the animousity directed at Mr. Francis. (???)

[BreathlessPerformance]

Alex, he was only stating the 1.6 vs 1.8 made a little more above 6500. Other than that I agree with what your stating.

Below about 6200rpm the 1.8 makes much more torque and hp. That is why they use a restrictor plate and get added weight.

[makus0025]

here is some math, I have an excel that I can change the inputs on. Let me know if any of the numbers should be tweeked like Tire diamter (I never measured it).

Tires 205/50R15
Diameter 23.07"
Circumference 72.47
Redline RPM 7000

Trans Gearing 1999 Max speed
1st 3.14 35.6 mph
2nd 1.89 59.1 mph
3rd 1.33 84 mph
4th 1 111.7 mph
5th 0.81 137.9 mph
Final drive 4.3

[BreathlessPerformance]

here is some math, I have an excel that I can change the inputs on. Let me know if any of the numbers should be tweeked like Tire diamter (I never measured it).

Tires 205/50R15
Diameter 23.07"
Circumference 72.47
Redline RPM 7000

Trans Gearing 1999 Max speed
1st 3.14 35.6 mph
2nd 1.89 59.1 mph
3rd 1.33 84 mph
4th 1 111.7 mph
5th 0.81 137.9 mph
Final drive 4.3

great, do you have it for the 1990 wit the slightly higher rev limit as well?