1991 1.6 Greddy - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-20-2006, 02:13 PM   #1
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Default 1991 1.6 Greddy

1991 1.6 M-5 @ 55k miles, Stock ECU, Stock Motor
Greddy turbo kit, Greddy downpipe, original 1.6 midpipe and cat, 2.75" "axle back" duals, Saab 900 i/c, BEGi FMU, 190 lph hp, 1.8 injectors, FM mbc, stock NGK gapped at .035", 13* pulling 6* with MSD

DynoJet, 23% humidity, 65*F, 3rd gear pulls:
6 psi--167 hp, 157 lb/ft
9 psi--185 hp, 160 lb/ft

I left 5 or 6 hp on the table, but wanted to remove a lean spot at 4.5k. I could not improve the fuel curve after 5.5k. I tried opening the BEGi's needle valve, advancing timing, and fooling with the afm clockspring. I could have added more boost and/or timing, but left a substanital safety area.
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Old 11-20-2006, 02:19 PM   #2
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looks good! Was the A/F sniffed after the cat?

got the .drf files to send this way?
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Old 11-20-2006, 02:40 PM   #3
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Quote:
Originally Posted by braineack View Post
looks good! Was the A/F sniffed after the cat?

got the .drf files to send this way?
No, their sensor was in my midpipe, pre cat, in place of my lc-1's sensor. I wish I had a run with my sensor for comparison. The graphs I got today look a lot like your graphs and lc-1 logs, and nothing like my lc-1 logs.

I didn't get any files, I didn't know to ask.
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Old 11-20-2006, 02:49 PM   #4
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There is smoothing applied to your dyno plot as well.
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Old 11-20-2006, 03:19 PM   #5
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your greddy is spooling VERY slow. You need to open up that exhaust man. Other than that it looks really nice...AFR's are rich across the board. The reason you only gained 3-4 ft/lb from 6-9psi is because you are spooling so late and the engine is out past where it would normally make peak tq (4000-4500) open up the exhaust and youll gain like 20whp and 20wtq.
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Old 11-20-2006, 03:30 PM   #6
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Quote:
Originally Posted by AndyFloyd View Post
your greddy is spooling VERY slow. You need to open up that exhaust man. Other than that it looks really nice...AFR's are rich across the board. The reason you only gained 3-4 ft/lb from 6-9psi is because you are spooling so late and the engine is out past where it would normally make peak tq (4000-4500) open up the exhaust and youll gain like 20whp and 20wtq.
Slow compared to other Greddy's? Or slow compared to other turbo/mani combos?

The exauhst mani and downpipe are Greddy. The cat and pipes for and aft of it are original 2". And I know that chokes the turbo.
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Old 11-20-2006, 03:40 PM   #7
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Quote:
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Slow compared to other Greddy's? Or slow compared to other turbo/mani combos?

The exauhst mani and downpipe are Greddy. The cat and pipes for and aft of it are original 2". And I know that chokes the turbo.
slow compared to other greddy setups. For example...my old greddy setup on 13psi made 230ft/lb and 217whp. That was with a large 15psi spike right around 4200 rpm ( that was full boost ). You can clearly see by your graph that you dont see full boost until around 5200-5500rpm. Thats VERY slow spool that will improve by over 1000rpm with a better exhaust and downpipe.
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Old 11-20-2006, 03:42 PM   #8
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yeah you should be making 100hp between 3.5 & 4k

time to call tony.
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Old 11-20-2006, 03:44 PM   #9
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now dont get me wrong, you have all the fuel well sorted out...but once you open up the exhaust youll run more lean under 4500 rpm. The reason you are around 12:1 right now is because the turbo isnt producing boost that low...so youll need to retune that rpm range...just so you know. But other than that your setup is making the power..it just needs to breathe
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Old 11-20-2006, 03:51 PM   #10
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it's probably the reason you 1.8s are doing a better job on your setup than they were for me.
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Old 11-20-2006, 03:56 PM   #11
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Quote:
Originally Posted by braineack View Post
it's probably the reason you 1.8s are doing a better job on your setup than they were for me.
likely
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Old 11-20-2006, 04:18 PM   #12
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Ahh... I wanted to make sure you thought it was laggy because of the original exauhst components, not because of some other fault hidden to me. I can do bigger pipes And that cat's _only_ 15 years old. You think the mani needs to be ported too eh? I'm sure I can have a machine shop do that for me. Is there anything I need to know? Your guidance is appreciated.

I spent a while studying others' dyno charts. I see where a big exahust will allow 100 hp sub 4k rpm, higher peak torque, and better power curves. I thought my peak tq was a little low.

Thanks
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Old 11-20-2006, 04:21 PM   #13
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Quote:
Originally Posted by Ben View Post
Ahh... I wanted to make sure you thought it was laggy because of the original exauhst components, not because of some other fault hidden to me. I can do bigger pipes And that cat's _only_ 15 years old. You think the mani needs to be ported too eh? I'm sure I can have a machine shop do that for me. Is there anything I need to know?

Your guidance is appreciated.

Thanks

The manifold would be just fine as is. Porting it wouldnt really give you any gains..that manifold is what it is. I found that when I took off my stock exhaust the cat was dead, yours could be as well. I bet if you cut out the cat and just welded a pipe in place of it you would spool 600rpm faster on just that alone. if you want to see how fast your car would be w/ a new exhaust take off the old exhaust completely and run open DP, youll love it trust me
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Old 11-20-2006, 07:52 PM   #14
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Your set-up is almost identical to mine. Sweet map BEN! Now you should take it to the track and get some times!
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Old 05-18-2007, 12:26 PM   #15
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Default New results, May 17 2007

You can compare this to my earlier 185 dynojet rwhp

Car is the same. Bone stock 91 now at 58k miles, greddy kit, 2.5" dp, RC 440 injectors, DIY dual feed rail, MSPNP w baro correction. Solid line shows the final run with MS EBC activated. The peak boost is a quick 15 psi spike settling to 14 psi. The dotted line is with MBC so you can see the difference.





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Old 05-18-2007, 12:40 PM   #16
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Wow, has to feel like a whole new car.

Want to cross post that graph in that recent MBC/EBC thread?....

Last edited by Splitime; 05-18-2007 at 12:40 PM. Reason: adding
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Old 05-19-2007, 09:34 AM   #17
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So why does torque drop after 5600 rpm? Let's look at the datalog:

2250: 1 PSI


3671: 5 PSI


3500: 14.5 PSI


4800: Boost Peak 15.2 PSI


5500: 14.5 PSI, starting to drop


6000: 13.8 PSI


6500: 13.3 PSI


6772 (peak rpm): 13.0 PSI


The decline in tq corresponds directly with the drop in boost. 227 lb ft at 15.2 psi dropping to 200 lbft at 13 psi. If we asked the EBC to hold boost at 15 psi, what would happen? Well, if I had a built motor I could carry more boost to redline and keep the torque curve very flat to redline. The HP curve would contiune on its steep increasing slope, though we're really starting to push the compressor, but there may be 270 rwhp in there. Also, it means that my power numbers with the MSPNP were made at 15psi spike dropping to 13psi. Impressive!

Last edited by Ben; 05-19-2007 at 09:47 AM.
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Old 05-19-2007, 07:39 PM   #18
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Damn, that makes me want megasquirt even more.
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Old 05-20-2007, 06:03 PM   #19
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do it steve you wont regret it no afm is sweet for sure.
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Old 05-20-2007, 11:43 PM   #20
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I figure if I go MS, I will have all the room to grow that I need. After I get out of the military and get set up pretty well, I want to go with a bigger and better turbo. I would like to eventually get to 400whp.
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