I had the same phenomena with the tailpipe sniffer. My dyno AFR shows an AFR in the high 13s whereas my LC-1 (which I re-calibrated the day before) was showing mid 12s. I guess a cat really does make a difference.

As for doing it again. Absolutely. Next spring more of you guys out there better come out!

 

Braineack are you and that other miata still runnig stock size rubber?

 

did they email the runs to anyone, if so can that someone email mine to me, i think they had toms name on them though, but they should be the only ~150hp ones. I really curious about my a/f ratio because everyone is saying they're a point off because of the cat, well i don't have a cat. what gives?

 

I think Bruce will be getting them sometime mid-week from the dyno guy. I think he didn't know how to e-mail the runs, but someone from the shop will during the week.

As for the AFR, theoretically b/c the cat uses up 02 in some of the reactions to reduce emissions, a post-cat AFR (such as a tailpipe sniffer) will be not as accurate as a pre-cat AFR depending upon how well your cat works. Since your car has no cat, your AFR should be pretty accurate.

 

Does anyone know how a Dynojet works? How does it take into account what gear you are in, or what tire size, or what rear end ratio? All I saw was an RPM pickup on a spark plug wire, and obviously it knows the drum speed. OK cool, it knows engine acceleration and drum acceleration, but your gear selection affects each. Obviously I have more "rear wheel" hp/torque in 1st than in 5th...I'm trying to think of a way the dynojet can calculate rwhp/tq regardless of gear selection with just those 2 inputs.

If he just entered the standard ratios from a 1992 miata (from some dynojet book/database???) then I guess my numbers are off because I have a 3.90 rear instead of the original 4.30's. I think Tom is running a 4.10 torsen too. What about tire size/diameter? I know my 16" toyos are about an inch larger in diameter than my 15" proxies. Thoughts?

 

I don't think the gear nor ratios matter too much for a dynojet as it measures power via acceleration at the wheel and uses the rpm to calculate torque. See the link:

http://www.bristoldyno.com/info/whatis.htm

I've dynoed a several times in different gears and the HP difference is 1-2HP at most, especially with the close ratio in the miata. It may be different in a car with longer gearing.

 

I've done the same on 2 dynojets. Ran a 3rd and 4th pull and saw no difference in the numbers.

Brad got a new fuel filter and said it's running better, but it stumbles in high rpms.

Can someone tell me why I didn't throw my MBC sitting in my passenger seat on for one run?


Once Brad gets a new pump and we think it's good to try again we'll go to a dyno locally and see what we can do. I'll try to run 10psi with 5:1 rise and see what she can do. Most likely with what I estimate 210/185.

If we get enough people next time, after we do our dyno tuning we should drive 20 mins south to Cecil County Drag Strip and have her a go! But hopefully we can get more members out, definitly a ton of fun!

 

Ahh yeah ok, duh.

 

Certainly isn't your age

 

Get a pressure gauge on there and pinch off the return to check the condition of the fuel pump.

 

Because you love complicated electronics so much and make sure you have as much of them in your setup as possible?


Sounds like fun. Plus, we can fill up on racegas at the Sunoco down the street on the way.

 

I have one, actually I had it there. Tell me why we didn't do it there?!

 

Probably because we all suspected the filter. With a clean filter, we can now check the pump.

 

damn i am jealous. guess i'll be putting off that big screen tv and throwing the money into the car for a change. nice numbers guys

 

#1 As if you don't throw money into the car(s)...

#2 The grass is always greener. Ever since I drove your original machine, I've been thinking about gutting my current miata to get it as light...

 

I wish I lived closer to you guys

 

Yes! Machine #1 was surprisingly quick N/A. Machine #2 will be scary with the GT28. It should be done by the next dyno day. haha.

 

Plots:

BrgRacer


TurboTim


OlderGuy


Braineack


Mach929


Newbsauce (Just couldn't get fuel :( )



Interesting Comparison: T3 S60 @ 9psi vs. GReddy @ 6psi

 

I noticed we all lose torque after 5.5k, would some sort of cam or cam gears cure this?

 

Well, you lose torque after 5.5k, but so does an S2000, until the second cam comes on: http://www.flyinmiata.com/tech/dyno_...99TvsS2000.pdf

Difference is, the S2000's valvetrain and engine are designed and built to make power at 8000+ RPM, while the Miata's is not.

I'd guess you'd have to a do quite a bit more work to take any real advantage of power at higher RPM. Or you could advance your intake cam timing one tooth...