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Discussion Starter · #1 ·
Here's the senerio----
I live in prescott Az, elevation is 5045ft.

I maybe max out speed at 125-130ish. I see others over 140.
I have everything done to my motor that is in my sig.

What could be wrong that i might be able to check myself. Im sure there are a few things, but if anyone could help...thanks

No Cel codes either.
EGR bypassed
Idle is always around 1750 RPM or higher. Cant get any lower. Trottle screw is all the way down, and i even had to rotate the disty to drop it more, but that has effected performance i think.
 

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offroad racing pipe or high flow cat

higher flow fuel pump

weight and aerodynamics key at those high speeds
 

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At such a high elevation the air is alot thinner u might want to think about having your timing adjusted and that could also fix your idle problem
 

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Just curious, why do you need to go faster than 110-120? I've gone 135+ once and I probably never will again. The car took too long to get up to that speed anyway.

What are your engine specs? I am pretty sure Wiseco doesn't make rods.

Why not turbo that beast? You have a suitable motor for it. Top speed doesn't mean shit if you can reach 100 before the other guy reaches 60.
 

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These cars arent ment to be driven that fast, and it takes quite a long stretch of road to get up to that speed, You dont measure your peformance by what speed it can go, but how fast it can get there. 0-60, 1/4 mile..
As far as some people seeing 140 or more, could have many things to do with it, including rim/tire size. I maxed out my mx6 a few times, and It was alwase hit higher speeds with thes stock rims. In reality, they might not be going that fast, but the speedo reads it
 

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Discussion Starter · #6 ·
I do know that elevation kills my performance because if i drive to pheonix, it runs alot stronger. Wiesco made the pistons, and the rods are mellenium S rods. I know going fast is bad and illegal, but my point is that is should go faster.
Cheif- read my info. I wish i could turbo, but compression is to high i was told. 10.2:1 and its bored over +20. I want to work on a set of heads, which is why i bought the ones from Cross. But i cant, no cams, and im not paying $500 for a set. My car is a daily driver too.

I am a pilot her at Embry Riddle. I get high altitutde training, so i do know the effects of the high elevation. ECU should compensate for it. I may have bad 02 or MAS. But no check engine lights. Anyways, i want it to be faster NA motor, and i already have a shit of stuff done.
 

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The computer cant change tha fact that there are fewer oxygen molecules per cubic foot of air.

BFGoodrich G-sports 215/35/18
^theres your answer. Your spedo will allways read slower than your actual road speed with larger tires .
 

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Discussion Starter · #8 ·
really, even though side by side the stockers are .5inch smaller?
 

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At any given road speed the taller tire will be turning fewer times than the stock tire. That means the the spedo will read slightly lower than the cars actual speed. Add in the stock tachs inherent inacuracy and losing 10 MPH in the 130-140 MPH range is likely.

And that dosnt account for the altered ratio between the engine 5th and final drive that will effectively rob the car of some torque. Since these cars are drag limited reducing wheel torque may also reduce top speed.
 

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^--- must of had some pretty big profile on the tread on your stockers.

Then again 35/18 compared to what 55/15 for stocks? Maybe reasonable.

With aftermarket wheels though, top speed measurements arent all that accurate especially when you are only talking 10mph or so between cars.

That idle could have something to do with it. Bad TPS would both not go as hard and screw your idle??? A TPS doesnt have to be stuffed to give a bad reading or be out of spec.
 

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Transmission could be different too. My pgt tranny only runs 130 or so where as the old mx6 tranny ran upwards of 150ish on flat straights. I think the speedos don't read right over 110 anyways. Don't feel bad I have a ZE that pulled 145 HP at the wheels. weak rigns i think. But it still runs the 1/8th in the high nines.
 

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A decent rule of thumb for a NA, spark ignition motor is that you can basically subtract 3% of your horsepower per 1000 feet above sea level. 15% loss is significant. I live in Denver, and feel your pain.
 

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Discussion Starter · #13 ·
I completely understand. its not good here at 5000ft, but Flagstaff is around 7-8 up to the peak where it is 12633ft. thats crazy.
 
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