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Track Whore
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1,120 Posts
Discussion Starter #1 (Edited)
This Saturday I decided to take my ITA race car to the dyno. At the last race weekend, I missed a shift and overrevved the engine and broke a rocker on number 1 intake cam. It effectively ended my weekend :(

I replaced the rocker and the cam and needed a palce to test the car. What better place than a dyno :D After running the car and making sure that all is well, I had some more dyno time to play around. So I decided to swap out my JWT ECU and test the G20 ECU and try different timing settings.

Here are the specs on the car

Engine: 98 lowport with 13K miles on it. Got it from a Junkyard for $700.
Cams: Stock 98 cams.
Intake: Short CAI with filter only; no pop charger allowed.
Header: OBX primary mated to a hotshot secondary. It is a perfect match. The OBX secondary is too small and forms a lip where it mates the OBX primary causing a restriction. The Hotshot secondary does not.
Exhaust: Short 2.25 inch pipe that dumps behind the driver with a little 15 inch long resonator to reduce the sound
Pulleys: 4 UR pulley set
Oil: Dino 10W-30. No I do not race on that oil.
Tranny oil: Shockproof heavy
Alignment: 3* negative; 1/8 toe out; maximum caster.
Gas: 91 octane 76 pump gas
Emission: No EGR; No Cat; All emission equipment removed and hoses plugged.

We did three runs for each timing setting. 2 runs in 4th gear and 1 run in 3rd gear. We wanted to do 4th gear since the G20 ECU does not have a speed limiter. We were able to hit 120 mph on the dyno :D

We first started the timing @ 15* BTDC, ie, like stock. I know some cars come with stock @ 13*, but mine came with 15* stock. So that is where we started. The car put down a best of 137 hp and 129 lb-ft. Not too bad considering the limited mods that we have.

Then we proceeded to advance the timing to the midpoint between the 15 and 20 timing marks on the UR crank pulley. We think it was around 17-18*. With this timing the maximum power was 141 hp and 131 lb-ft.

The third and final advance was to 20* BTDC. That is as far as I have ever advanced the timing on the car with stock cams. I was just curious to see if there were any gains going above 17-18. The car laid down 143 hp and 132 lb-ft.

I wanted to advance some more, but I did not want to push the limits of 91 octane gas. Had we had 93 octane gas in CA, I would have pushed the timing higher just to see if there are any gains to be had beyond 20*

The best power gain was around 5700 rpm. The car gained ~ 9 hp and 8 lb-ft simply from advancing the timing from 15* to 20*. That is impressive with such little mods.

Below is the dyno curve of the three best runs from each category. for some reason the signal pickup on this dyno was braking up at the high rpm end, but we still got the max power that the car was putting. The numbers are uncorrected since all the runs were done on the same day and minutes apart.



And below is the AFR for 3 4th gear runs with the timing @ 20*. The G20 ECU has a very nice AFR curve until 6700 rpm. Then it falls below the desired 13:1 and can end up as low as 11.5:1 by redline. It does not show on this table, but I have other tables that show just that.

 

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Professor Dingbat
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5,543 Posts
So I decided to swap out my JWT ECU and test the G20 ECU and try different timing settings
Just curious as to why you swapped out the JWT ECU. Don't you think there might be something to be gained by optimizing timing with the JWT ECU?
 

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Registered
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1,005 Posts
The RR motor also loves timing.... this dyno was done with a stock motor cai 3 inch cat back stock cat and timing in 19,5 on stock p11 obd1 ecu

 

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Track Whore
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1,120 Posts
Discussion Starter #6
Good numbers! And nice find with the 13K engine. That's lower than 99% of JDMs.
Thanks. I found that engine in NY and had it shipped to me. Alas, during shipping the engine tipped over and the valve cover broke as well as the injector harness. Luckily, I had spares. I will never ship with Roadway again. Yes, they are cheap, but they did a crappy job. The reason I got this lowport engine is because ITA rules do not allow me to run a high port since the 200SX never came with one.
 

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Track Whore
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1,120 Posts
Discussion Starter #7 (Edited)
excellent results for an IT legal engine!
Thanks Mike. Now imagine if ITA allows me to run 91 cams. This engine would rock. I have this theory that 91 cams in a low port produce more power than in a high port. Does that make sense or am I just flat out wrong?
 

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Track Whore
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1,120 Posts
Discussion Starter #8
Just curious as to why you swapped out the JWT ECU. Don't you think there might be something to be gained by optimizing timing with the JWT ECU?
I tested the JWT ECU and run that ECU when racing. I am still testing the JWT ECU and I am going to test two JWT ECUs (one for stock cams and one for S3/S4 cams) on a road going SE-R and then test the with the G20 ECU. Until then I am holding off on the results.
 
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