Heading to the dyno - tips??

J

JIgou

New member
Heading to the dyno on Friday afternoon to do a bit of testing and tweaking on our Spec Miatas.

Even though this is an IT forum, I know a bunch (well, a few, anyway) of you guys have done this with your cars; I haven't, and am looking for some general tips/advice.

Here's the plan:
Taking my car, plus two other SMs
-- Mine is a 1.6, we'll have another 1.6 and a 1.8.
-- Taking several airflow meters to swap/test with (1.6 cars only)
-- Taking cleaned/blueprinted injectors from local shop (1.6)
-- Taking timing light to find the sweet spot for each engine (all)
-- Will have three people to swap/test/move cars
-- Planning on 2, maybe 3 hours, total

Goals:
1. Get a baseline for each car
2. Find the optimum base timing for each car
3. Match up airflow meters between the 1.6 cars
4. Determine optimum shift points based on torque/HP curves
5. Walk away with graphs and numbers to evaluate later

Anything I'm missing? Any advice? What DO I need to do to make this worthwhile?

I'm particularly interested in the "determine optimum shift points" item. I know it should be done....but haven't had a chance to get my brain around it yet....

THANKS!!

Jarrod
 
Based on my experience on the dyno, 2-3 hours probably won't be enough. I was only able to make about 3 pulls in one hour, as the car had to cool down between each pull.


------------------
Bill
Planet 6 Racing
bill (at) planet6racing (dot) com
 
Maybe too ambitious. Dyno time is expensive.

I think Grassroots may have had an article on this. While you are obviously planning ahead, I can't see more than finding a good timing setting in the time alloted.

How long does it take to swap injectors and those air flow meters?

You may land up doubling changes in order to fit the time, which can defeat the idea of establishing a true baseline.

I thought it would be interesting to throw on some illegal parts (e.g., adjustble cam pulleys) to get a base line to set the engine the same with legal parts (offset keys).

Good Luck!
 
Airflow meters are maybe 5 minutes the way the cars are set up....so no big deal.

Injectors are a little more involved, but still pretty quick. They're kind of an afterthought, and may get nixed as we get into the time.

I DO know that they're not booked up afterwards (starting at 1:30), so we should have the option of running longer if we determine the need. Sounds like we might....

Thanks for the heads-up on the time involved!

Jarrod
 
try get a run thru the gears dyno plot.. It shows how when you shift the car moves the RPM and Hp levels.. Often there is more hp lost by not doing this than gained.. Remember you dont only race in 1 gear!
 
The only thing I would add is to plan a schedule to maximize your time. Know exactly what changes you will make and in what order you will make them. If you waste time scratching your head trying to decide which item you want to try next, you are only costing yourself money. But hey, the dyno guy will be happy!

------------------
Chris Wire
Team Wire Racing
ITS Mazda RX7 #35
[email protected]
 
Can you adjust fuel pressure in SM?

You only need to let the car idle for about 2-3 minutes between pulls on a dyno to get similar numbers.

I'd say do two or three pulls to get a baseline and then start making adjustments.

The only thing I can tell you is that when we dynoed our cars we made adjustments and added about 2 hp.

So you can figure out if it is worth it.

Jamie
 
Bring spares and tools to change things out. You'll probably find one car runs better than the others, so you might want to swap things around to eliminate variables.

Use the exhaust sniffer if they have one. Print or right this info down.

Extra new plugs.

Bring a DVOM for checking AFM and O2 voltages(etc), infrared pyrometer for temps around the engine, "dial back to zero" timing light for checking total advance. Careful: Miatas fire through each wire twice and a sensitive timing light will pick the second firing up-halving your advance number.

If they don't have a large fan for the front of the car(they should), jump the fan relay. A plant squirt bottle for misting the radiator will help cool it down quick.

If it's a Dynojet or similar roller dyno, note your rear alignment specs, tire size, type of wheel, and chassis height(off the dyno and strapped to the dyno) for each car.

If it's a loaded chassis dyno, note the "ramp" time.

Have fun. Be careful you don't get addicted to the dyno. Come back and post your numbers.
smile.gif
 
So, how'd it go? Good goals. I'm planning to do the same over the winter.

Scott
SM#52

QUOTE]Originally posted by JIgou:
Heading to the dyno on Friday afternoon to do a bit of testing and tweaking on our Spec Miatas.

Even though this is an IT forum, I know a bunch (well, a few, anyway) of you guys have done this with your cars; I haven't, and am looking for some general tips/advice.

Here's the plan:
Taking my car, plus two other SMs
-- Mine is a 1.6, we'll have another 1.6 and a 1.8.
-- Taking several airflow meters to swap/test with (1.6 cars only)
-- Taking cleaned/blueprinted injectors from local shop (1.6)
-- Taking timing light to find the sweet spot for each engine (all)
-- Will have three people to swap/test/move cars
-- Planning on 2, maybe 3 hours, total

Goals:
1. Get a baseline for each car
2. Find the optimum base timing for each car
3. Match up airflow meters between the 1.6 cars
4. Determine optimum shift points based on torque/HP curves
5. Walk away with graphs and numbers to evaluate later

Anything I'm missing? Any advice? What DO I need to do to make this worthwhile?

I'm particularly interested in the "determine optimum shift points" item. I know it should be done....but haven't had a chance to get my brain around it yet....

THANKS!!

Jarrod[/QUOTE]
 
The visit is done. It was, of course, a rather enlightening experience.

The 1.8 car decided it didn't want to play. (The other guy owns both it and the other 1.6, so it really WAS the car that decided this one....must not have spoken nice enough to it in the days leading up to the visit....)

Tests run on a Mustang dyno. The guys running it have only had it for a couple of months, so they're still getting used to it.

Garage/open building. About 90 degrees, 50 percent humidity. Total time on dyno - 2.5 hours. They were nice and rounded us to 2 hours.
biggrin.gif


AFR measured by a wide-band O2 sensor hooked to a Motec box, then plugged into the computer. Attached to end of tailpipe.

All pulls done in 4th gear, 1:1 ratio in a Miata.

Pull #1 yielded 131 horsepower. YEE HAW!

Then the guys changed the multiplier factor in the software, and we ended up with another pull yielding 96.9 HP/82.1 ft-lb at 6750 RPM. More realistic, I suppose....dangit. Of course, with 131 HP I'd have a hard time explaining why I haven't won every single time I've touched a track....

Did that baseline with my car, a known quantity. ('91 Miata, straightpipe plus resonator for exhaust, open air filter slapped on end of airflow sensor, 900 miles (10 or so races) on untouched Mazda crate motor, installed last winter). Note the RPMs - they cut the run off a bit short on that one.

Switched to the other 1.6 - pulled 93-ish HP (don't have his stats). Decided to swap airflow boxes - found tape covering half the opening, upstream of the airflow sensor. Whoops. Fixed tape, different airflow sensor: 97-ish HP. Much better.

Note: tape across half of intake loses 4 HP.

(This car is also a 1.6 - has a 300-mile motor with about 4 races on it. The motor came from a well-respected builder. VERY well respected. OK, VERY VERY well.....you get the idea.
wink.gif
)

Swapped through the three meters (two spare, plus the two on each car), noting AF measurements for each. All ratios ended up within half a point of each other. I know mine ended up at 12.6 at the top end of my best run.

Pulled that car to swap injectors, and put mine on to try different meters.

After selecting the "best" meter for mine (turned out to be the one I was running), we threw on a meter from an RX-7 for kicks. Immediate 5.7 HP gain, zero torque gain. The torque peaked MUCH later with the 7 airflow meter, and the car was generally sluggish at all but high RPMs.

One final pull on mine, we bumped the timing up to 18 degrees. Gained 0.6 HP, 0.7 ft-lb. - ending at 100.6 HP at 7250 and 84.8 ft-lb at 5500. As mentioned before, AFR worked its way down to 12.6 right before the fun-limiter kicked in.

Meanwhile, the other car was getting fresh injectors. Put it back on, and gained a couple tenths in each area, but still pretty much even (within .5 on each) with my car.

THEN the guys running the dyno asked each other who had input the weather correction information....and neither had.

SO, after they plugged in the temperature and humidity levels, the other car picked up about 4 HP and about 4 ft-lb. Not a huge deal - we were able to make some adjustments and confirm some things we already suspected. At least they didn't figure that out and do it in the middle without telling us.

Overall, it was a good trip. There are claims floating around the SM site of an exhaust that adds 4 hp and 7 ft-lb, but there's no mention of what that's compared to. If we can get some research done and figure out what that exhaust is, we might pop for another visit in the near future; otherwise, I think we're done at the dyno for the year.

Comments?? Even though we've already gone, I'm still very interested in learning what we might have done wrong or can do better next time....

Jarrod
 
Originally posted by JIgou:
The visit is done. It was, of course, a rather enlightening experience.

The 1.8 car decided it didn't want to play. (The other guy owns both it and the other 1.6, so it really WAS the car that decided this one....must not have spoken nice enough to it in the days leading up to the visit....)

Tests run on a Mustang dyno. The guys running it have only had it for a couple of months, so they're still getting used to it.

Garage/open building. About 90 degrees, 50 percent humidity. Total time on dyno - 2.5 hours. They were nice and rounded us to 2 hours.
biggrin.gif


AFR measured by a wide-band O2 sensor hooked to a Motec box, then plugged into the computer. Attached to end of tailpipe.

All pulls done in 4th gear, 1:1 ratio in a Miata.

Pull #1 yielded 131 horsepower. YEE HAW!

Then the guys changed the multiplier factor in the software, and we ended up with another pull yielding 96.9 HP/82.1 ft-lb at 6750 RPM. More realistic, I suppose....dangit. Of course, with 131 HP I'd have a hard time explaining why I haven't won every single time I've touched a track....

Did that baseline with my car, a known quantity. ('91 Miata, straightpipe plus resonator for exhaust, open air filter slapped on end of airflow sensor, 900 miles (10 or so races) on untouched Mazda crate motor, installed last winter). Note the RPMs - they cut the run off a bit short on that one.

Switched to the other 1.6 - pulled 93-ish HP (don't have his stats). Decided to swap airflow boxes - found tape covering half the opening, upstream of the airflow sensor. Whoops. Fixed tape, different airflow sensor: 97-ish HP. Much better.

Note: tape across half of intake loses 4 HP.

(This car is also a 1.6 - has a 300-mile motor with about 4 races on it. The motor came from a well-respected builder. VERY well respected. OK, VERY VERY well.....you get the idea.
wink.gif
)

Swapped through the three meters (two spare, plus the two on each car), noting AF measurements for each. All ratios ended up within half a point of each other. I know mine ended up at 12.6 at the top end of my best run.

Pulled that car to swap injectors, and put mine on to try different meters.

After selecting the "best" meter for mine (turned out to be the one I was running), we threw on a meter from an RX-7 for kicks. Immediate 5.7 HP gain, zero torque gain. The torque peaked MUCH later with the 7 airflow meter, and the car was generally sluggish at all but high RPMs.

One final pull on mine, we bumped the timing up to 18 degrees. Gained 0.6 HP, 0.7 ft-lb. - ending at 100.6 HP at 7250 and 84.8 ft-lb at 5500. As mentioned before, AFR worked its way down to 12.6 right before the fun-limiter kicked in.

Meanwhile, the other car was getting fresh injectors. Put it back on, and gained a couple tenths in each area, but still pretty much even (within .5 on each) with my car.

THEN the guys running the dyno asked each other who had input the weather correction information....and neither had.

SO, after they plugged in the temperature and humidity levels, the other car picked up about 4 HP and about 4 ft-lb. Not a huge deal - we were able to make some adjustments and confirm some things we already suspected. At least they didn't figure that out and do it in the middle without telling us.

Overall, it was a good trip. There are claims floating around the SM site of an exhaust that adds 4 hp and 7 ft-lb, but there's no mention of what that's compared to. If we can get some research done and figure out what that exhaust is, we might pop for another visit in the near future; otherwise, I think we're done at the dyno for the year.

Comments?? Even though we've already gone, I'm still very interested in learning what we might have done wrong or can do better next time....

Jarrod
Click to expand...


Correct me if I'm wrong but isn't that a ton of HP for a miata. when Ken payson and serge and all the other SM guys up here in NE did the dyno testing at LRP they where only in the high 80's. Why the huge difference? was yours measuring at the wheels?
 
If you were using a chassis dyno, (drum style) the way the car is strapped, the tires, the air pressure, etc all make a difference.....

Consistency is key.

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Originally posted by lateapex911:
If you were using a chassis dyno, (drum style) the way the car is strapped, the tires, the air pressure, etc all make a difference.....

Consistency is key.
Click to expand...

Jake,

You saw the one at Lime Rock right? It was actually bolted directly to the rear wheels with the tires taken off. Trick setup and portable as well! I thought it was pretty neat since it got rid of all the straps and chances for the wheels slipping and all the variables that go along with the tires.
 
I don't know that it's a ton more than we should have expected. I suppose it's possible that the operators (remember, they're still pretty new to the machine) still had an incorrect multiplier plugged in.

It was indeed at the rear wheels. I believe it was this model: http://www.mustangdyne.com/ChassisDyno/md250.htm

Car had pretty old (over a year) Toyos on it, inflated to 36 lbs. (Target coming off the track is 39-40 hot).

Ive heard numbers around 110 from some of the folks down in Texas, but that's on a different dyno, on a different day, with a different operator.......

Jarrod
 
The dyno at LRP was a VERY different type, and supposedly is more consistent/accurate than others (or so Stephan told me). The way the one at LRP works, you jack up the car and attach apparatus to the hubs rather than tying it down. Seemed to work very well, and Stephan said they aren't as expnesive as the in ground types (and obviously portable)...anyone in the NER wanna buy one for all of us?

Eric
NER SM #02
 
Speaking of consistency, the correction factor must be correct for every single run. A rise in 2-3% humidity or 5 degrees in temperature could account for a 1% Hp difference or more. Don't have my correction factors in front of me.

The operator's math maybe a little off as well.

Your 96.9HP/82.1Ft-LBS at 6750 doesn't work.

Either you had 96.9HP and 75.4Ft. LBS at 6750

or

You had 105.52HP and 82.1Ft/LBS at 6750

or

The 96.9/82.1 numbers are peak at different RPMS.
 
Yup- Not only did I see it, but I did a few pulls on it.

Interestingly enough, the hp figure matched within 1%, (106.23 vs 105.4) the number I got off a chassis dyno a year and a half ago!

This on a 12A rotary that I traded an old Saab 9000 with bad engine mounts for. I was told it was a minty mint motor built by Charlie Vaccaro (of NYR E prod fame), but the guy who traded me is known to streeeetch the truth, so the insides are unknown.

I agree that bolting the unit to the axles eliminates some factors, therefor increasing repeatability, and eliminates some, (but not all) potential for operator error. He told me it was a non-inertia style unit. I noticed garden hoses hooked to it for a water supply. I am unclear as to it's capability to back out the drivetrain's influence from the net number, as you can do with a roller style (interta based) chassis dyno. Which is useful for changing drivetrain parameters for lower drag.

I suppose you could still do that, if you have confidence in the repeatablity of the pulls and you don't make any engine changes between runs.

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Jarrod,

Thanks for the info. You can pick up some more power if you can "somehow" get the a/f a little leaner up top.

Payson's car was around 88 that day at LR. The best SM pulling over 96. Ken won, so what's that tell you?

The dyno at LR was a Dyna-Pak. It holds a load on the hubs as an engine dyno loads the crank. IMO it is a better way to go and gives more realistic ENGINE output numbers. The inertia dynos are just that, any change in the intertia of the drivetrain will show as more horsepower. This is useful also, but adds variables when comparing engine hp numbers.

I believe the Mustang does also load the wheels, but I'm not sure.

Matt Kessler

[This message has been edited by MK (edited August 27, 2003).]
 
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