NC with Cosworth making only 150 hp????

[fredmuggs]

I went back and looked at your original post where it says you have an automatic tranny. Maybe that is not able to transmit all the new torque. Since the engine has boost and rich fuel, the engine must be making high power.

i am just guessing as I am not experienced in SC or automatic trannys.

Keep us informed.

Thanks for your interest:
Back in March '11, I did some research and it appears the AT in the Miata is the same as that used in the RX8. Here's that info

Found from four (unvalidated) sources that the AT in my '07 Miata should be SJ6A-EL (Miata '06 - '08) which is also used in the RX8 ('06-'09).
First source Level 10, which offers value body rebuild for $600 to sharpen shifts. Level10 says the trans is not controlled by the ECU, but by a separate trans controller which they can reflash or supersede for DOLLARS.
Second source: http://www.transtec.com/selector_guide/Mazda.htm
Third: http://www.autotransparts.com/MazdaTransmissions.html
Fourth: http://amtrans.nl/mazda.pdf
If the SJ6A-EL is, in fact, the correct trans, and is also used in the RX8, it should take a lot of power right out of the box. With a very little tricking, it should take a lot of really hard use.

Seems to me, to "lose" 50 HP in the drivetrain would require that the HP/torque must be going one of three places
(1) burned off in slippage -- but the trans isn't slipping: sound tach, etc.
(2) "detuning" through timing and/or fuel to reduce output. When we look at the fuel and timing logs, this is not apparent. The numbers go where the calibrator tells them to go.
(3) burned off in the torque converter. I can't think right off how to check that.

Thanks, Ted928 for the input. I'll see what I can find out about the converter issue.

PS:
Brian -- you know a Mazda Rep who might be willing to give some input on the trans?

[fredmuggs]

Measuring back pressure at the O2 Sensor shows 2 lbs.

OK, let me ask the stupid question. I've never seen a back pressure measurement quoted before -- how is it done? What are the test conditions, and the measuring device? What values are considered "good" or "bad"?

Hi, jboemier:

Thanks for your interest.
I asked, and the shop put a pressure gauge on the bung for the O2 sensor, which is located between the two converters (both still in place).

I think you may be onto something. Seems to me, measuring pressure between the converters might tell us about the rear converter, but not the front. I'll follow up with the shop and have them pull down the exhaust at the manifold. They should be able to visually inspect the front converter from there. I've also come up with an idea for the rear converter. Kind of a "standard fix," if you know what I mean.

Good question.
Thanks,
Fred

[fredmuggs]

Hi, Brian:

At one time, there was a recall of this Cosworth kit. Do you know what that was about? Do you know anyone over at Cosworth who might lend some insight?

Thanks,
Fred

[fredmuggs]

Seriously... reach out to Jay. He knows his stuff and is working with some Cosworth owners and their troubles... You can find him here and in miata.net as blackone....

Hi ON-ARC"

I must be in the wrong fourm or something over at miata.net. Couldn't find a "Jay" or "blackone."

Just before I email the Moderator over there, do you have any additional contact info for Jay?

Thanks,
Fred

[jboemler]

By "pressure gauge", do you mean the same fixture that's used for leak-down testing? I somehow doubt that's a valid test, since it's intended to measure something that's almost fully sealed, using very small flow numbers. With the rest of the exhaust very open by comparison, the flow required for any meaningful value would have to be much larger than the leak-down fixture can provide. I also wonder how much the potentially open valves in the head would distort the readings.

Basically, I'm just not sure your 2-pound number means anything at all, but willing to be convinced.

[fredmuggs]

Seriously... reach out to Jay. He knows his stuff and is working with some Cosworth owners and their troubles... You can find him here and in miata.net as blackone....

Ha!!! I found him.

Thanks,
Fred

[jboemler]

Seriously... reach out to Jay. He knows his stuff and is working with some Cosworth owners and their troubles... You can find him here and in miata.net as blackone....

Hi ON-ARC"

I must be in the wrong fourm or something over at miata.net. Couldn't find a "Jay" or "blackone."

Just before I email the Moderator over there, do you have any additional contact info for Jay?

Thanks,
Fred

Here's Jay's member info:
http://forum.miata.net/vb/member.php?u=25738

[fredmuggs]

By "pressure gauge", do you mean the same fixture that's used for leak-down testing? I somehow doubt that's a valid test, since it's intended to measure something that's almost fully sealed, using very small flow numbers. With the rest of the exhaust very open by comparison, the flow required for any meaningful value would have to be much larger than the leak-down fixture can provide. I also wonder how much the potentially open valves in the head would distort the readings.

Basically, I'm just not sure your 2-pound number means anything at all, but willing to be convinced.

Hi, jboemler:
After talking with the shop, I am having them pull down the exhaust pipe and visually inspect the front converter -- best they can. I don't know if one can actually see all the way through the front converter -- the one that's built into the exhaust manifold. Presumably, there is a way to inspect and even replace that unit, short of replacing the manifold. Will have to research that.

I'll let you know what we find.

Thanks again,
fred

[jboemler]

It'll be interesting to see what they come back with. My recollection is that you can see the first converter from the bottom, without removing the header. Not sure that you could see THROUGH it enough to truly inspect it, but I doubt you'll be able to see it at all from the top. You may find that you don't get any benefit from removing it, but hopefully others will jump in on that score.

BTW, in talking about the shop's measurements, I didn't mean to imply that there was an undiagnosed blockage in your system -- I have no indication one way or the other.

[fredmuggs]

I went back and looked at your original post where it says you have an automatic tranny. Maybe that is not able to transmit all the new torque. Since the engine has boost and rich fuel, the engine must be making high power.

i am just guessing as I am not experienced in SC or automatic trannys.

Keep us informed.

Sorry, jay928, my response of a few days back apparently went somewhere else.

On the AT, I tried some research a while back. Here's part of that post.

Found from four (unvalidated) sources that the AT in my '07 Miata should be SJ6A-EL (Miata '06 - '08) which is also used in the RX8 ('06-'09).

First source [of info on the NC AT] Level 10, which offers value body rebuild for $600 to sharpen shifts. Level10 says the trans is not controlled by the ECU, but by a separate trans controller which they can reflash or supersede for DOLLARS.
Second source: http://www.transtec.com/selector_guide/Mazda.htm
Third: http://www.autotransparts.com/MazdaTransmissions.html
Fourth: http://amtrans.nl/mazda.pdf

If the SJ6A-EL is, in fact, the correct trans [in the NC], and is also used in the RX8, it should take a lot of power right out of the box. With a very little tricking, it should take a lot of really hard use.


The only place the power could go is "absorbed" into the converter or the trans control unit is telling the ECU to back off. There's no apparent slippage in the trans and no variation in the tach, so I doubt the first. The second, calibration parameters, don't show anything untoward in the DashDyno logs the tuner and I looked at.

That does not mean you are wrong about the AT.

Thanks,
Fred