Speed's boosted NA6

[beavis]

Stopper looks great in black

It was my understanding that the NB ABS cars had no proportioning.
The MX-5 is generally front bias heavy, particularly in the earlier year cars.

Can you detail exactly what your brake setup is now?
You could very likely resolve your issue with a more aggressive rear pad?

[speed]

Can you detail exactly what your brake setup is now?
You could very likely resolve your issue with a more aggressive rear pad?

Thanks Brendan,

Fronts are 276mm sports discs and calipers from 2002 NB (maybe 2001) onwards, with Akebono pads. I'd never heard of akebono until I now.

Rears are stock NA6 231mm discs and calipers with Girling pads.

I'm not sure what the Booster/Master cylinder was off. Electrical plug was different to NA6 but otherwise the unit looks the same. There is a comparison pic earlier in this thread.

My NA6 brakes worked well but you'd really have to apply decent pedal pressure to emergency stop quickly.

The current setup requires far less pedal pressure from dabbing to locking up the fronts.
I "squeeze" the brakes too so was surprised at the difference but obviously the fronts do have more surface area now.

I have read about using more aggressive rear pads but suspect I'd also need greater disc/pad surface area

Matching rear brakes are 276mm but I'm not sure if caliper is unique to the sports brakes or if same as other NB's with a larger carrier. Pads are definitely larger.

Comments appreciated. Thanks!

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[speed]

I don't know for sure, I'm currently pain-killered off my face until the dentist can fit me in in like two weeks. BUT.

I recall seeing a lovely graph on (i'm pretty sure) mt.net which has the differences in the prop valves for NA/NB/NB ABS - ABS is linear but the NA/NB are only linear to a point, then they become more front-loaded.

https://www.flyinmiata.com/tech/stock_bpv.php

OK, I found it, it wasn't mt.net.

As an aside, on my car with the 1.6 prop valve and the 1.8 brakes, the fronts do seem to do way more work when I'm standing on the pedal. I've not pushed it to lock-up (on a good surface) but with the brakes and AD08s and progressively (but quickly) standing on the pedal to get the weight to transfer up front, it drops a lot of speed quite rapidly, but I can hear the front tyres biting into the road. But at the moment with the smallest factory rears, and the biggest factory fronts, you're quite possibly in the middle of the Chaos Zone (tm).

Thanks for that. Sorry you're experiencing dental pain. I'd rather bamboo under my finger nails then that!

I need more coffee before I attempt to go thru the link. Other posts I've read heavily mention knee curve. Honestly I don't know what that is yet.

Will have a read after I get Mrs Speed off to work.

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[speed]

I'm taking a break from brakes for the moment.

Since my car is up on the hoist I thought I'd check my ride height. The lowest point is my exhaust. I made it that way to clear the bigger diff but that was before i had installed it. Seems i made way too much clearance.



With a straight edge across the ramps (and if I alter the height of the exhaust hangers) the rear section can be easily modded to 100mm clearance from the ground.



The issue is where the dump pipe meets the cat and the cat itself. It measures 95mm.



In order to gain the additional clearance, I'd need to chop and re weld the section where the dump meets the cat.

Now I know this, I'll get stuck into it next week.







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[speed]

Some ND OEM goodness for my NA6.
Please excuse the dusty and dirty wheels!

Now my car is part NA6, NA8, NB8b/c, ND, Toyota Yaris and Nissan Silvia.

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[StanTheMan]

Shes a barstard child hu?

have you thought about heat expansion?

does alloy expand more than Cast iron?

[speed]

have you thought about heat expansion?

does alloy expand more than Cast iron?

No I haven't but alloy does expand more than cast iron but I figure you're aware of that. It's an interesting thought and I cross my fingers that future speed doesn't have issues with wheels disintegrating whilst driving.

My theory is that my alloy head has a cast iron exhaust manifold bolted to it with a very hot turbo slapped on the side and the head is fine.

My wheels see more ambient temp than my engine bay does. Fingers crossed!

I'm also aware of another person with the same wheel and brake set up and they've not reported any issues.

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[bruce]

It would not heat up that much, it's not an F1 car.

[StanTheMan]

It would not heat up that much, it's not an F1 car.

you are probably right. ive just become super cautious since i had my pistons hit the head on Patchy

[speed]

you are probably right. ive just become super cautious since i had my pistons hit the head on Patchy

But wasn't that after you machined a fair bit off the head or did something break?


Unfortunately, I now have other issues...

A mate stopped by and he hasn't seen the car since it was supercharged.

So naturally I had to take him for a drive around the block (It's okay guys I didn't stack it!), we're in the car and I go to give it some as it boosts and the horsepower just cuts violently. Slow down and try again and same thing. At about 4,500rpm the car basically will not go. It won't pass a certain rev or psi.

I'm thinking fuel pump or filter, maybe injectors but the way it happens, somehow feels electrical, I can't describe it.

So I guess I'll pull the spark plugs first and also check the cops and their connections before I move onto fuel. I've not touched the tune since it was done, so that should be fine.

Is just crappy when I've done bugger all kays since it was tuned. Something is not right.

Stay tuned and wish me luck

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[bruce]

I'd say spark plug leads, but you've got COPS.

[rascal]

Might not be related, but I had a similar annoyingly random issue with mine (running COPS as well so not coilpacks) that would cause same symptoms, a sudden and violent lack of acceleration. After much troubleshooting my issue ended up being a hairline crack inside the wiring for the MAP sensor which would randomly lose connection, causing the ECU to think I had lifted my foot off the accelerator and remove all fuel. Not nice when you actually have your right foot buried in the firewall..

I only managed to find it once it got worse and would do it in neutral in the shed.
I then manually revved it whilst wiggling all the wiring and finally traced it down to the MAP sensor wiring. Cut out the dodgy wiring part and redid it and (touch wood) 4 years on all is still good.

[speed]

I'd say spark plug leads, but you've got COPS.

After much troubleshooting my issue ended up being a hairline crack inside the wiring for the MAP sensor which would randomly lose connection, causing the ECU to think I had lifted my foot off the accelerator and remove all fuel. Not nice when you actually have your right foot buried in the firewall..

Thanks Bruce and rascal,
Turned out to be spark plugs.

Pulled them out to see this...





Cleaned them up and threw them back in.





Gradual to 70% throttle = no issues.
1st run, gave it full throttle from 3k and it was much better but acceleration power cut around 5k but nowhere near as bad as yesterday.
Gave it a few more runs. The 2nd attempt was better again but issue mildly present.
Third run onwards and no issues.
Gave her about 10 runs all up.

Thank god for that. Am going to keep an eye on it as I really was expecting a wring issue as rascal described.

Will pop back in to see the tuner as the car runs richer than I'd like at idle and low throttle. AFR reads 12's everywhere and can be 11's briefly when on full song.

It's the range from idle to cruising at low throttle that bothers me.

I'm also wondering if I should be going from the BKRE7's back to 6's.

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[speed]

Cleaned up some wiring. May remove the bracket later.

Before:


After:


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[Cus]

Check sure you're not using a fancy rev limiter curve - Mine catches me out when I forget about it (rev limit rises with CLT, and then drops off once I'm over 105C)