Expected power figures

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benckj
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Re: Expected power figures

Post by benckj » 12/02/20 18:07

I’ll see if I can locate the old links on ECU code.

Generally it’s factors you cannot control which will catch you out on engine detonation. Above avg ambient temp, sub grade fuel, ignition fault, boost spike or unbalanced injectors can mean the difference between driving and walking. Can push the envelope so far before seams pop.



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Re: Expected power figures

Post by benckj » 12/02/20 19:53


benckj wrote: ↑
Wed Feb 12, 2020 1:54 am
Stock ECU will run lean on centre two cylinders under high boost which may not show on the wideband located in dump pipe. Someone on the MR2OC actually broke the OEM code and found a fault with the ignition advance on cyl 3. Table also runs out of MAP values so it interpolates above max values which can cause unknown problems. I could go on but the link provided above should serve as a warning to others.............. Link to this discussion?

For those of you interested in the ECU codes. This link explains quite a bit including the differences between US/UK and JDM model ECU's. Note Post 8 and short interpretation about ignition advance (or lack of) in cyl 2.


https://www.mr2oc.com/threads/gen3-3s-v ... st-6611601

Happy reading,
Jim

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Re: Expected power figures

Post by jimi » 12/02/20 21:11

AFAIK it was Jeremy Ross (from the UK) who originally reverse engineered the ECU codes and Jon Sole (also from the UK) who continued the work.
The original thread on ECU code disassembly on TwoBrutal which is referred to in the thread you posted the link to is still viewable. Although TwoBrutal is no longer active the forums have been archived to keep all the information in the forums available. http://www.woodsport.org/forum/showthre ... isassembly

Incidentally Jon Sole is a member of this club https://www.mr2oc.co.uk/forum/members/22689.html
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Re: Expected power figures

Post by MR2DI4 » 13/02/20 4:06

Would not want to push the Rev 2 to 19psi. You can push it to 17psi but that is about it.

You can do the math from the stock fuel pressure spec of 27 to 31psi (vac lines connect to the FPR) at idle is the Toyota spec that is safe for the stock boost of 10 psi.

I'm running on 32psi fuel pressure sitting at idle with all the vac lines connected the stock "Rich under boost" condition of 10:1 AFR is GONE at 17psi of boost.

32 -27 = 5psi so you add 5 to the 10psi of boost and you have 15psi still rich and anything above 15psi your starting to run leaner than the Toyota spec. 17psi of boost and I'm seeing AFR's in the 12's so 19psi could be getting nasty and I wouldn't go there.

Mine has been running 17psi since 2008 without an issue so you can call that a decent reliability test.

Pretty much the ECU is flying blind and its unlikely there is any engine mapping over 13psi (stock fuel cut) so what your essentially doing is controlling the AFR with fuel pressure alone.The injectors will be maxed out on full duty cycle and your crossing your fingers they are still balanced on all cylinders.

However, the setup in mine is no longer "Idiot proof" I only run Mobil 8000 fuel which is 98 and you need to monitor the fuel pressure gauge all the time and the boost guage. If anything changes its going to go bang in short order. The car has NO FUEL cut anymore for any form of overboost condition.

I also have to admit if I rebuilt the head the flow would increase and I probably wouldn't need to run 17psi to get the same power. Boost pressure and actual flow are not the same, they are related by the resistance to the flow and the biggest bottleneck in the system are the valves, even more so dirty valves. The inlets in mine are going to be pretty bad by now. Less boost is also less exhaust backpressure so again more power its a win win.

Would be pretty "censored" if even just a head rebuild and port work didn't gain another 20Hp at the top end as this is really where the change in flow comes into play and probably 15psi would be pushing in as much air as 17psi was doing before the rebuild, maybe even less required than that, however "More Air" overall is not really an option its all maxed out in terms of fuel to go with it.

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