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Interesting Rev 3 ECU information. http://www.gt4dc.co.uk/forum/viewtopic.php?f=13&t=6863 |
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Author: | Nibbles [ Tue Dec 10, 2013 11:48 am ] |
Post subject: | Interesting Rev 3 ECU information. |
From the MR2OC. jon.sole wrote: The ST205 ECU has a lower fuel cut at higher revs. The Rev 3 MR2 ECU has the same fuel cut across the rev range. jon.sole wrote: Both ECUs have a table of 3 values that controls the fuel cut limit at 3 rev ranges. On the MR2 ECU the 3 values are the same: Code: ROM:C1EF table_boost_limit: .dw 0200h ROM:C1EF ; Boost cut lookup table ROM:C1F1 .db 02h ROM:C1F2 .db 218, 218, 218 ; 255 on TechTom ECUs ROM:C1F5 On the ST205 the last entry is reduced, which has the effect of reducing fuel cut progressively from 4800rpm to 6400rpm: Code: ROM:C1B8 .dw 0200h ROM:C1BA .db 02h ROM:C1BB .db 218, 218, 205 I don't know the exact conversion from the raw values in the table to PSI, but it is around a 5% drop at 6400rpm. I'm guessing the lower fuel cut at higher RPM is to protect the transmission. Modified ECUs with a TechTom board fitted change the values in the table to 255 to effectively remove fuel cut. shinny wrote: Assuming 0 means 0V from the map sensor and 255 means 5V and based upon Richard Doig's formulas (http://gtfour.supras.org.nz/mapsensor.htm) I calculated the MAP sensor's voltages...
1.31bar -> 19psi -> 4.27V -> 218 1.14bar -> 16.5psi -> 4.02V -> 205 That puts the ST205's fuel cut at 1.14 bar, which is lower than I expected! I didn't have trouble running 1.15 bar on my original external wastegate setup and the ST205 ECU, so perhaps Richard's formula is fractionally incorrect? Edit: This page suggests the ST205 has fuel cut set at 17psi / 1.17bar: http://k1ano.co.uk/boostcontrol/rvgt4specifics.htm |
Author: | TrackToyFour [ Tue Dec 10, 2013 11:47 pm ] |
Post subject: | Re: Interesting Rev 3 ECU information. |
Interesting post.....not sure exactly what it all means in reality. Needs a universal translator or a cold cloth on the forehead |
Author: | Sirius [ Tue Dec 10, 2013 11:52 pm ] |
Post subject: | Re: Interesting Rev 3 ECU information. |
Yep very interesting. I'm not sure that any of the measurement kit most of us have fitted will have greater real time accuracy than about 0.1 bar so 1.14 1.15 I don't think there is any real way of telling. |
Author: | Diceman [ Wed Dec 11, 2013 10:27 am ] |
Post subject: | Re: Interesting Rev 3 ECU information. |
Interesting info There could be a host of reasons. Gearboxes are normally rated for maximum torque capability I thought with only cooling requirements being greater at higher rpm? I would initially suspect it is more to do with the turbo efficiency and preventing lots of hot air entering the engine. |
Author: | Nibbles [ Wed Dec 11, 2013 11:25 am ] |
Post subject: | Re: Interesting Rev 3 ECU information. |
I've already commented on the MR2 thread that I don't think it's transmission limited. I think your turbo theory makes sense, but then why would the MR2 not be limited. |
Author: | two_OH_five [ Wed Dec 11, 2013 12:30 pm ] |
Post subject: | Re: Interesting Rev 3 ECU information. |
As the mr2 runs less power it might well be consuming the same amount of air at higher boost than compared to a 4 |
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