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 Although TwoBrutal is no longer active the forums have been archived to keep all the information in the forums available.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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Re: Expected power figures

Post by Sonac » 27/02/20 15:19

MR2DI4 wrote:
12/02/20 16:49
Coming from an electronics background i have my doubts that there are any significant problems with the stock ecu. The firmware was constantly revised which is evident by part number changes. I went to great effort to keep the turbo pressure sensor signal integrity right up to 17psi in my fcd design when everyone else insisted the ecu didnt even use it for anything other than fuel cut and the boost gauge.

Running lean under boost is what kills your engine. As long as your chucking enough fuel in there you can tell the car is running right or not. The stock ecu is awesome its never missed a beat.
I've glad to hear it. I actually have a FCD laying around. Should I plug the stock turbo pressure sensor back in and use that instead?

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Re: Expected power figures

Post by MR2DI4 » 27/02/20 19:01

Sonac wrote:
27/02/20 15:19


I've glad to hear it. I actually have a FCD laying around. Should I plug the stock turbo pressure sensor back in and use that instead?
Depends on which one it is. I remember doing some research at the time and because they are all a bit generic and designed to fit to multiple manufacturers and not specific to the MR2, I decided to make my own.

The HKS one is pretty good. I went with their SLD (Speed Limit Defender so now the 180km/hr top speed limit is gone) in my car as its much harder to make and includes a micro and coding which is not my area of expertise.

That really cheap hack that simply uses a Zener diode does not work, or I should clarify, it works for the speed cut itself but does NOT maintain the integrity of the signal from the TPS to the ECU due to the electronics design of the output from the TPS and input on the ECU. All it does is permanently pull down the Voltage to a set level so its the same as just pulling the TPS vac hose.What you get is a fixed Voltage in this case all the time the engine is running and it doesn't go from about 2.6V (at 0psi or less under vac) all the way to 4.1V (full boost) so IF the ECU actually uses this signal in the mapping you just stuffed it. I say IF because nobody really knows so if you keep the right signal going into the ECU as Toyota intended, then your obviously safe.

Fuel cut on the Rev 2 occurs at about 13psi or 4.2V from the TPS. The TPS actually continues to output a very nice linear Voltage signal right the way to 17.5psi if you put in a FCD where it hits the 5V supply to it with a maximum output of 4.8V. All a decent FCD does is keep the exact same input to output signal until 4.1V and then the output FLATLINES to that 4.1V so it never gets to the cut threshold of 4.2V.
Last edited by MR2DI4 on 27/02/20 23:04, edited 1 time in total.

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Re: Expected power figures

Post by Sonac » 27/02/20 21:55

I see. Mine is HKS yes. I think I mostly understand what you mean with the voltages.

So the HKS will basically do the same as pulling the vac hose. So no point installing it then.

That's a lot of good info. Thanks!

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Re: Expected power figures

Post by MR2DI4 » 27/02/20 23:03

Sonac wrote:
27/02/20 21:55
I see. Mine is HKS yes. I think I mostly understand what you mean with the voltages.

So the HKS will basically do the same as pulling the vac hose. So no point installing it then.

That's a lot of good info. Thanks!
Well not quite, the HKS maintains the intended Voltage to the ECU, pulling the vac hose (0psi effectively) gives about 2.6V only from memory to the ECU the whole time the engine is running and of course you also lose the stock boost gauge. The stock boost gauge actually works really well once you go increasing the boost. At 17psi it bounces off the top and responds much faster.It comes down to whether or not you think the ECU uses that TPS in the engine mapping or not. Kind of eliminates the need to worry if it does or doesn't with the HKS fitted. If I had one just lying about doing nothing then I would fit it.

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Re: Expected power figures

Post by Sonac » 03/03/20 17:47

MR2DI4 wrote:
27/02/20 23:03
Sonac wrote:
27/02/20 21:55
I see. Mine is HKS yes. I think I mostly understand what you mean with the voltages.

So the HKS will basically do the same as pulling the vac hose. So no point installing it then.

That's a lot of good info. Thanks!
Well not quite, the HKS maintains the intended Voltage to the ECU, pulling the vac hose (0psi effectively) gives about 2.6V only from memory to the ECU the whole time the engine is running and of course you also lose the stock boost gauge. The stock boost gauge actually works really well once you go increasing the boost. At 17psi it bounces off the top and responds much faster.It comes down to whether or not you think the ECU uses that TPS in the engine mapping or not. Kind of eliminates the need to worry if it does or doesn't with the HKS fitted. If I had one just lying about doing nothing then I would fit it.
I'll fit it soon then. Thanks. I dont use the stock boost gauge anyway. Its been replaced with a proper one.

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Re: Expected power figures

Post by jimGTS » 04/03/20 18:13

Sonac wrote:
10/02/20 12:54

I do plan on getting my car on a dyno at some point but what kind of power should I be expecting at this boost level? From what I read on one guide should be about 300whp right?

Thanks!
maybe on a dynojet, which is likely what your reading on a US forum.
you wont be making anywhere near that on a UK dyno WHP wise.

my car with the 20b dynoed 255whp (dyno dynamics), and i suspect was upwards of 260-265whp when i was posting faster 1/4 mile times than US cars running 330-350whp on a dynojet (similar trap speeds which is best indicator of power).



i suggest get a power run done, id expect your running 230whp at best on a gen2 engine at that boost level.
200-210whp is pretty normal on a ct26 at 15psi.

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Re: Expected power figures

Post by MR2DI4 » 04/03/20 18:35

Yes I would agree with Jim on the power figures pretty much got 225hp on mine. Would make the 250hp but would need head work and exhaust change. 300 not possible with Gen 2 the injectors are to small.


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Re: Expected power figures

Post by FirstMidship » 28/03/20 19:50

When you're trying to make more power, it's worth looking at the higher performance injectors as stated as well as a higher pressure fuel pump. No good having all that boost with standard injectors and a standard fuel pump.
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Re: Expected power figures

Post by MR2DI4 » 29/03/20 0:14

You will find that the car ends up making no more power at 19psi as it does at 17psi.

What your better off doing is rebuilding the engine and doing some serious port work and matching along with cleaning up the valves and vastly improving the flow.

What you will then find is the car makes as much power at 15psi as it did at 17psi.

Its not all about pressure its about actual airflow. Things start to go backwards in power beyond a certain point, your wategate remains closed and the exhaust back pressure builds trying to make more boost. Improving the flow will get you that same power at 15psi as you had at 19psi on an old engine thats never been rebuilt.

Pressure and actual airflow have no direct relationship in the engine. Take the worst case scenario, your inlet valves are closed so you have full boost but no airflow. The valves are actually your biggest restriction by far and hence the massive gains coming from VVT.

Awesome video here.

https://www.youtube.com/watch?v=WwlNqaz9q_0

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