Setup is 90 miata with 1.8 diff
gt2860rs @13psi
3" exhaust from downpipe back
195/60-14 tires
im 180lbs and did the run this morning at 72f and a baro of 30

what am i missing here this is way to high

 

Correct gear?

 

so much torque the curves never cross. you've effectively defied the laws of..........well everything

 

did this one on my lunch break in 3rd gear. also changed the final drive to 3.9 and got way more realistic numbers. Even though 400 would be awesome on only 13psi

And both together

Blue is the 4th gear pull with corrected final drive and red is 3rd gear

 

3.6 & 3.9 make about 35 whp difference in your case. do you know which it is?
Mine runs a 4.1:1 1.8 diff

 

I don't is there any marking on the diff? I can check when I get home

 

How much did you pay for your diff. Is it a Torsen?

the 3.63 would generally carry a premium as they are not USDM

 

1.8 diffs came in 4.3, 4.1, and 3.9 in the US, 3.6 available in Australia.

When you swapped the diff, did you also swap the speedo gear in the transmission? If not (and if the speed is still correct), then it's a 4.3.

--Ian

 

most likely 4.3 or 4.1

 

Just for ***** & Giggle Ive plotted your plots against mine which are both 1.6's. But Mine is N/A

But have you noticed how the plot goes a bit whohooooo.....over 5000 rpm? when there is no smoothing applied?



I was thinking its my spring being old & worn out and running high lift cams.They just don't like it & have gone pair shape. Not necessarily jumping or anything just generally being toast.
but yours does the same thing. So maybe its nothing too be concerned about. could be just the software?
Other suggestions have been cam timing & My china Rx8 copy Ebay injectors

either way, Ive had a set of 65lbs springs sitting there which are going in this weekend . Will see how it goes

 

intersetingly I never swapped my speedo gear when I installed the 4.1 diff.
I run slightly taller tyres than the OP but only a tiny fraction.
comparing with the GPS my speed is dead on. Or at least it looks that way looking at the speedo.

 

My friend got it when the car was his project I think he spent 500-600 on it

 

A 3.6 ring & pinion is $600 for the parts and $200 to set it up, so a Torsen with one installed usually sells at a significant premium to a normal Torsen.

--Ian

 

Miata speedos are off by quite a bit stock and read about 5% fast. Then going from a 4.3 to a 4.1 will be about a 5% decrease in the speedo, so in your case it worked out great.