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View Full Version : Mazda Miata 1.6L Dyno Results - Two Cars



Ron Earp
10-18-2005, 01:35 PM
Dyno Results

My partners and I were recently able to dyno our two SMs back to back and were able to collect some interesting data. The cars have the following vital specs:

#43 - Just built on a 1990 192k mile car. Engine has never been opened and the only major services have been clutch (race clutch), rear main seal, timing belt change, as well as new water pump and alternator. Car has a homemade exhaust that is fairly restrictive with some fairly crappy kinks in the pipe after the downpipe. Intake is a $5 cone filter on the AFM directly. Plug wires are not original, but they are not new from me putting them on either. The car only has about 6 hours of track time total.

#39 - We've had this car for over a year. 1990 car and has a 120k mile engine that has not been opened. It does have a race clutch and new transmission, and the only other things that have been done are timing belt change and a good exhaust that is free flowing as well as the intake that curves under the AFM (can't recall the name). Timing is set to 14 BTDC and the AFM is stock, never touched or opened. This car has well over 60 hours of track time, including 13 at last years' Charge of the Headlight Brigade and 7 hours getting me through school in January.

The dyno used was a relatively new Dynojet located here in Raleigh NC at Haywood Custom Performance, a Ford specialty shop and I've know the fellow Randy there for years. Good place. Air temps were about 76F and humidity about 50%, a nice day.

The results:

#43 was up first and made 100hp even and 92 ft/lbs of torque. The pull showed the car was quite rich at WOT at anything over about 4k RPM. We adjusted the AFM slightly with attempts to lean the engine out a bit and it definitely helped, rear wheel hp went up to 105hp and torque hopped up to 96 ft/lbs. After that change we had a look at timing be the motor did not want any more timing - 12, 14, 16 all caused power to drop, and naturally so did 8 degrees just for sake of checking. I suspect that we have a restrictive air intake and exhaust since it just won't respond to any timing changes. Hard to say. At any rate, I was reasonably happy given that the car has known intake and exhaust restrictions.

#39 was up next and made 114 hp and 101 ft/lbs of torque. The plot showed that this car was running significantly leaner at WOT above 4k RPM than #43. We only fiddled with the ignition timing on this car and found that 14 was optimal for it, losing a couple of hp when shifted from 14 degrees BTDC. Since we were pressed for time we did not try anything else with the car since we were pretty happy with the results.

All in all it was a useful session. I'll make some changes to #43 and get it back on the dyno and see if we can improve the numbers. Both cars are running in the 13 hr VIR Enduro that is coming up so look us up there. I'll post the dyno plots as soon as I can get them scanned, but they are nothing really exciting. Any comments are welcome, but don't jinx us by saying "Holy cow, those motors are going to blow any day!"

Ron

lateapex911
10-18-2005, 11:32 PM
Great stuff, Ron, and no, they won't blow....ever! Those things are pretty reliable, LOL. Just keep them in good fresh oil, and make sure your timing is right and you should be fine.

Thanks for posting, I wish others were so open!

I can't remember, has the jensen been on the rollers?

Ron Earp
10-19-2005, 07:03 AM
Originally posted by lateapex911@Oct 19 2005, 03:32 AM

I can't remember, has the jensen been on the rollers?

62962


No, about the time we figured out the machine work on the head was crap I started this SM build, August 1. The SM was done by Oct 2 but needs a few monor things for the 13 hour enduro that I am attending to now. Once the endruo is over we'll concentrate of the TR8 and the JH. The TR7 is making some power - over 200 ft lbs of torque and it had a miss and wouldn't rev over about 4k!

JeffYoung
10-19-2005, 07:37 AM
Dynos are interesting tools. Cheaper than a test day for collecting data and trying to make the motor run right.

Jake, drove an IT7 car for the first time a few weeks back. A hoot, I liked it. Can you give me general "power" specs for those cars? It seemed quicker than I expected.

With the Miatas, we did expect far more gains/losses from timing adjustments than we saw. It may be that No. 39 is optimized for the motor we have, and for No. 43 the exhaust and cheap intake are making the timing adjustments have little or no effect.

zracre
10-19-2005, 08:27 AM
114 hp is an awesome number for a well used motor...i have seen some built motors put out about the same up to maybe 118 to 120...

JeffYoung
10-19-2005, 08:37 AM
Evan, thanks for confirming that. We have a split amongst the partnership -- one of us wants to buy a built motor. I'm of the mind that 114 is pretty damn good.

Have you seen anything much over 120?

History on this motor is pretty funny. We built the car in a rush for the 13 hour at VIR last year. Ran it briefly at a track day before hand. At the 13 hour, we had a shifter bushing go bad, and would miss the 3 to 4 upshit (selecting 2 instead) on a fairly regular basis (probably happened 5-7 times). That motor saw 9k rpm at least that many times. Car never missed a beat.

Got it ready for Ron's school in January, drained the water and...FULL of oil. We kind of scracthed our heads, since it was right before the school, filled it up with water and sent Ron out. Another 6 hours of flawless running.

Car ran four race weekends, a test weekend and a rental weekend this year, with only a problem with the clutch and tranny.

I'm not a big fan of Miatas, but damn, that is some reliable shit right there.

Limey
10-19-2005, 10:08 AM
[quote]
Evan, thanks for confirming that. We have a split amongst the partnership -- one of us wants to buy a built motor. I'm of the mind that 114 is pretty damn good.

Jeff, only when the motor starts getting tired....I'm happy with it at the mo'. We'll see how she's feeling after the 13 hour ;-)

....and talking of horsepower.......I believe I was able to get up to 5th in the races at CMP last weekend (but couldn't hold it there!) - but no chance of catching those 4 front-runners. I was watching my in-car last night and in Heat 1 on Saturday, first lap, turn 8 - there were several cars out on the dirt, track left. One of the front-runners re-joined the track and by then I was about half the back-straight in front of him. I got passed on the start finish line by him and he went past like I was going backwards.......I'm not exactly a newbie, but that's an awful lot of talent to make up that ground in less than half a lap.......maybe I need more seat time...? ;-)

Mark

zracre
10-19-2005, 10:24 AM
[quote]
Have you seen anything much over 120?

the highest claim i have heard of is 123hp from a well broken in sunbelt motor...i know people that have bought high mileage examples for good $$. i would keep that gem as long as it makes that power...a typical high mileage unit makes 105 to 110hp...good luck!!

mavis
10-19-2005, 10:22 PM
I'd say 114 is pretty good too. I have an engine which is supposed to have 45,000 miles on it which came from a junkyard. With a $5 cone filter and homemade exhaust I got 108 out of it. It was really hot that day and the dyno did not have a lambda sensor so I have no idea how lean or rich it was running. I fiddled with the timing a little and it did not seem to make much difference. I've talked to other folks who have similar engines with about the same results. Racing it in ITA puts me near the front in this division but ironically WAY further back in SM.
Any thoughts on what a fully-prepped IT motor would make? I'm guessing if the Sunbelt guys can get 120 out of a "stock" motor, a fully prepped IT car could get maybe 10-5% more. I might be way off.

RacerBowie
10-20-2005, 07:29 AM
Originally posted by mavis@Oct 19 2005, 10:22 PM
I'd say 114 is pretty good too. I have an engine which is supposed to have 45,000 miles on it which came from a junkyard. With a $5 cone filter and homemade exhaust I got 108 out of it. It was really hot that day and the dyno did not have a lambda sensor so I have no idea how lean or rich it was running. I fiddled with the timing a little and it did not seem to make much difference. I've talked to other folks who have similar engines with about the same results. Racing it in ITA puts me near the front in this division but ironically WAY further back in SM.
Any thoughts on what a fully-prepped IT motor would make? I'm guessing if the Sunbelt guys can get 120 out of a "stock" motor, a fully prepped IT car could get maybe 10-5% more. I might be way off.

63030


My "fully prepped" (sans ECU work) IT 1.6 Made 125 whp on the dyno 2 years ago.

In those 2 years, SM motors have found about 7-8 hp, going from "114 is the best you can get" to "I have 121, but I heard about a guy with 123"

When I get my motor rebuilt, I will be pretty bummed if I don't see 135. That will be with a custom ECU.

Andy Bettencourt
10-20-2005, 07:58 AM
Having talked to one of the top builders, expect 125-130 from a 1.6 and 140 from a 1.8 with top prep.

WHP (dynojet)

AB

RacerBowie
10-20-2005, 03:09 PM
Originally posted by Andy Bettencourt@Oct 20 2005, 07:58 AM
Having talked to one of the top builders, expect 125-130 from a 1.6 and 140 from a 1.8 with top prep.

WHP (dynojet)

AB

63051


Yep, that is why I am aiming for 135! :023:

oanglade
10-25-2005, 05:12 PM
Go get 'em Bowie!!

:023: