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Thread: Hitting 13AFR, anyone ever ran 9.5:1 map on 8.5:1 setup?

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Posts: 1-10 of 17
2008-06-20 21:53:40
Hitting 13AFR, anyone ever ran 9.5:1 map on 8.5:1 setup?
Installed my aem uego wideband last weekend and have been hitting 13AFR under WOT at the top of the gear... it will progressively increase from 12.5 to 13 at the top of the gear.
So far I haven't been able to figure it out yet, fuel pressure looks to be just fine but am questioning my jwt chip. It is supposed to be for z32/555/9.5:1 and I am running z32/555/8.5:1. I would think that the difference in compression would just make the car running a little more or less agrressive on the timing but I thought that would be it.
I am at this point thinking my injectors are flowing properly.

Has anyone ever had problems running lean with their JWT setup that is similar to mine?
2008-06-20 23:09:03
depending on how much boost your running will make a difference. With my safc 370cc @ 3bar with my 9.5:1 motor with s4's i was maxing my injectors out on 8psi of boost. ive got other things done also but no matter what changes i did to the safc it would not get any richer. During the main part of the powerband from low through mid it would stay steady 12.5:1 A/F on the wideband. after about 6500 rpms it would increase to 13:1. I never had any detonation, The car pulled like mad crazy, ran a 13.0@110 on a T25 on 8psi. Thats how well it ran. I think your A/F is fine if your not getting any detonation as long as your running low boost. Now im running a 4bar 370cc setup and running 14psi and its even crazier under full torque band around 4500-5k rpm it is crazy, it will break the tires loose in third at around 50mph till about 65-70mph. Its pretty rediculous. At that point i think im coming pretty close to maxing the injectors out completely at that peak torque.

I know JWT setups tend to be a little quirky from hearing peoples past experience but if it runs good leave it. If you up the boost then you will need to have those a/f ratios down to 12:0-12.5 steady. At topend for it to lean out a little bit wont hurt and will actually help your topend power
2008-06-21 02:41:46
Did you check fuel pressure at top end? It might be the fuel pump maxed out or damaged.
2008-06-21 03:46:54
he cant watch the fuel pressure and boost and afr at the same time.
2008-06-21 07:02:09
Originally Posted by Jerimiah
he cant watch the fuel pressure and boost and afr at the same time.

Lol so do them one at a time no big deal
2008-06-21 13:08:38
I would be nervous to run that lean under boosted conditions. I would try bumping the fuel pressure by 10-15lbs. See where it takes you. Make a pull, then adjust some more. Always want to start rich and work leaner.
2008-06-21 15:13:06
You can check the pump easily by raising your fuel pressure, if the car still leans out then you have a bad filter or pump. If it gets richer by changing the fuel pressure then you know the pump is good.

This is assuming you aren't maxxing those injectors out. Cause you need to be making about 350whp to do that, and if so my VET sucks. lol
2008-06-22 18:48:59
ahah I would hope the 555cc are good for more than 350whp .

I am going to try a few things this week to see where it gets me. Hopefully something stupid lol.
2008-06-23 22:15:02
Im running stock U13 det/12 psi/s4/3" exhaust on a jwt ecu for 9,5:1 and Im on the rich side. Bought a Nismo afpr and had to bring it down to 2.7 bar to get at least 1:12 a/f. So deffently not running lean on a 9,5:1 to 8,5/1 combo.
2008-06-24 02:21:24
You say you had to decrease your fuel pressure in order to bet 1:12? What was it previously? I have my fuel pressure turned up pretty high right now.
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