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With the 4.875 rear end you'll be way way way under 60mph at the top of second. You'll be forced to use 3rd and shifting too often at an Autox sucks. Every shift is basically going to cost you 0.5seconds
 

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With the 4.875 rear end you'll be way way way under 60mph at the top of second. You'll be forced to use 3rd and shifting too often at an Autox sucks. Every shift is basically going to cost you 0.5seconds
Yet, they set TTOD with this setup. Funny how that works, huh?
Come on folks. Real world > internet analysis.

I know one thing. This is a car worth standing in line for at MMRLS this year.
 

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Discussion Starter #23
With the 4.875 rear end you'll be way way way under 60mph at the top of second. You'll be forced to use 3rd and shifting too often at an Autox sucks. Every shift is basically going to cost you 0.5seconds
Unless you can easily do the whole course in 3rd because it has so much power. We chose this gearing for the track, where it rocks. San Diego ax courses tend to be very fast. Note how deep I got into 4th, about 80mph.

Other parts of the country have dinky little lots where you barely hit 60, we could still use 3rd with this engine and gearing. What hurts is if you don't have enough power for the taller gear and have keep down shifting to 2nd and back to 3rd. Most stock-ish class 4 cyl cars fall into this trap so a tall 2nd is better there.

For every comment before and after this post questioning how well it works on the street..it doesn't. Sucks on the street and I don't care. I built it to hoon and fitted appropriate gearing. This is not a commuter :)
 

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Umm a slow shift might take 1/2 second. Decent ones are like 1/2 of that.

Having said that, they don't cost in course time, what it took to shift. Since you are still moving at the time.
 

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Nice work as always Emilio!

I'm curious about the t-stat placement-- I assume it's due to spacial restrictions for the ITBs? Did you drill more than a 1/16" hole in the t-stat since it's so far away?

I'm planning out an Mtuned kit on my NB1, had a non-Mtuned reroute on an NA prior and was curious about temp differences w it isolated from the engine. I have measured w an infrared (not sure how accurate compared to actual water temp within) the OEM upper rad hose and found it's pretty consistent with minimal variance from the water neck to rad inlet-- if anything the t-stat cover has a cooler surface temp.
 

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Discussion Starter #30
Umm a slow shift might take 1/2 second. Decent ones are like 1/2 of that.

Having said that, they don't cost in course time, what it took to shift. Since you are still moving at the time.
Our data shows our best syncro box (OEM trans) shifts are about 150ms. During that time the car is decelerating. So ones setup must have better ratios so the cars stays closer to peak power everytime the drive demands max torque. So yeah, lots of gears work just fine if you can shift quick and the ratios allow a high rpm engine to stay in a narrow powerband. If you have enough torque to over power the available traction at all RPM like a Corvette on street tires, one gear does just fine.

Nice work as always Emilio!

I'm curious about the t-stat placement-- I assume it's due to spacial restrictions for the ITBs? Did you drill more than a 1/16" hole in the t-stat since it's so far away?

I'm planning out an Mtuned kit on my NB1, had a non-Mtuned reroute on an NA prior and was curious about temp differences w it isolated from the engine. I have measured w an infrared (not sure how accurate compared to actual water temp within) the OEM upper rad hose and found it's pretty consistent with minimal variance from the water neck to rad inlet-- if anything the t-stat cover has a cooler surface temp.
Yup, not enough room further back.
 

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Still, saving say 0.2 seconds on a shift is a good thing, however it does not save you 0.2 seconds on overall course time.

Just run the motion equations for autocross speeds and distances.
 

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Discussion Starter #32
Still, saving say 0.2 seconds on a shift is a good thing, however it does not save you 0.2 seconds on overall course time.

Just run the motion equations for autocross speeds and distances.
You're assuming the power variable is a constant to make the generalization. That would be misleading to anyone reading this that does not have a full understanding yet.

A low revving 150whp engine with a broader powerband might be fastest with a wider ratio 5 speed, only because it eliminates a shift or two. The 200whp narrower powerband engine might be faster with an additional ratio.

Internet speculation and math aside, we have collected quite a bit of data over the years on our race cars. When we were restricted to a 5 speed and powercapped, we built engines with dead flat power bands wide enough to span the gaps in ratios. When we were not restricted in the transmission, we shaped a different powerband.

Trans have a 2300rpm drop between gears? Build an engine with a 3000rpm powerband.
This car was fastest with a 5 speed because it was designed to.


This car was fastest with a 6 speed


Some of this might shed light on why I ask what transmission and rear end a person has in their car when they ask about cams or BP4W vs BP6D head. On a street car, the gaps are merely annoying. On a race car, well, you lose a lot. We are pretty good at winning :hello kitty:
 

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Discussion Starter #35
Do you guys have a date/time lined up for the dyno yet?
Planned for tomorrow afternoon but it's too hot. Hit 101° here today. Dyno bay faces the sun and it would be around 97° when we strap the first car down. Three cars to do, Sonny's SuperMiata for a 140whp race map. Mental, Johns C30-94 Rotrex BP6D that should put down around 320whp on pump gas and Taxi. Anyway, too hot so we rescheduled to next Tues AM as we're in no particular hurry. Wunderground forecasts 67° Tues am which sounds much better.
 

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Sounds good.
Sounds like Sonny will be SPM'n it at Laguna for mmrls?

Or are you not having a race on Sunday this year?
 

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Discussion Starter #37
Sounds good.
Sounds like Sonny will be SPM'n it at Laguna for mmrls?

Or are you not having a race on Sunday this year?
No race cars this year. Focusing on giving rides in our 3 cars. The ND project car, Taxi and Deviate the 250whp K20 powered car. SuperMiata next weekend at Buttonwillow and Sonnmy is second in points.
 

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Discussion Starter #38
205whp

Ran out of time on the dyno but got it pretty close. Another 5-10whp once we play around with injection timing, ex cam timing and fine tune VVT tables a bit more. Motor is for sale BTW. Email us directly if you are interested. We can build you something as simple as a blueprinted stock BP or anything in between.
 
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