cafcwest

Yup, what limits the vert to the 115mph top speed? Is it a different ECU than coupes? Would swapping ECU's 'fix' it? Or is it something else?
Thanks,
-Jayson

1987RX7guy

iTrader: (3)

Lack of power. There is no governer on any FC that I know of in the US. If you have the power you can keep going untill you run out of gears and redline.

Erk

Verts are just alot heavier then other models of FC.

ponykiller

I can get my 91 vert to 130.

Verts are limited by a higher Cd (Coefficient of Drag), and a greater mass. I would assume your 'vert is an auto if you can only get it to 115, or is an S4. If you get a cone intake and replace your cats with a straight pipe, you should be able to get to ~125.

hpram99

I've been up past 125 (spedometer speed) probably around 117 (real speed) in my s5 vert. I'll let you know how 2' of 3" straight pipe affects top speed when I get my engine back together

Icemark

Top speed is around 125 in stock verts. It is only limited by gearing and aerodynamics, not by anything electrical

KiyoKix

Icemark is correct, it has nothing to do with weight either. Weight determines acceleration not top speed.

ponykiller

More weight means larger frictional force at the tires. This means more resistance to both acceleration and top speed (when limited by power).

cafcwest

I thought I had read in an old Motor Trend that the vert were limited to 114mph, thats why I questioned. The car seems to pull quite hard and then just stop right there.

venomrx7

Is it an S4? My 1990 vert goes well past that with the stock ECU. I hit about 136 on the highway last night racing a neon, so it will go past 114.

Tofuball

I've done 120 something. :/

NZConvertible

This is true, but the rolling resistance of the tires is a tiny, tiny fraction of the overall forces that must be overcome. At high speed they are so small compared to aerodynamic drag they are not worth considering.

The only reason why the 'vert would be slower than the NA coupe is aerodynamics.

RotaryResurrection

iTrader: (8)

I'd say the change in CD and weight both affect the vert's top speed.

I have had my convertible up to 151mph, had 1krpm to go until redline, and have a witness who I scared the **** out of...

downwinddave

Depends on how long the hill is.
AND how big your ***** are.

NZConvertible

The 'verts ~15% extra weight would be lucky to have a 1-2mph effect. The maths proves it's all about aero.

RotaryResurrection

iTrader: (8)

Yes, on a straight stretch, you are right. KNowing how slow verts are in stock form, it would take 2-3 miles or more to get up to top speed. How many of us can say we can travel 3-4 miles without encountering a hill? As soon as you hit that grade, even a slight one, weight comes into play.

ponykiller

While I agree that the additional frictional force due to weight is small compared to the aerodynamic drag of the car, it is still there and still will make a difference. This is why I originally stated both mass and Cd as the reasons for decreased top speed.

RotaryResurrection is correct about the hills and the increase in mass having a larger effect when moving up the hill.

NZConvertible

The power required to overcome drag force due to weight on the tires inceases linearly with speed. The power required to overcome drag force due to air resistance inceases to the third power of speed. I don't think people appreciate the massive difference that makes.

While you are technically correct to mention weight, in reality it's almost irrelevent. The effect of the extra weight of the 'vert has a miniscule effect on top speed when compared to the effect of the higher Cd.

And top speed isn't ususally measured on a hill...

Sam

151.. pretty good. hopefully when my Turbo Vert is fixed and tuned I can do that : )

ponykiller

Wait a minute.... Are you sure?

JKM

Best post ever.

andrew lohaus

why do these "top speed" threads always end up having to explain that weight has baisicaly no influence on top speed.

to simplify

top speed=hpXgears Vs. drag(mostly aero)

we clear?

anyway i think the main reson the vert is down on speed is that it doesn't share the coupe's slippery .29 c.d.

oh and you should probobly have the top up. i dont think anyone mentioned that yet. (i guess ill be the wise ***)

Bukwild

before Kevin and me swapped a t2 into my s4 vert I used to hit 130 no probs.

Icemark

Only the 86-87 Sport had a .29 Cd, all the other coupe models have around .31 Cd.

The vert has .33 Cd top up, and .38 Cd top down.