Peter Day

Yamaha FZR750R OW01  & YZF750 specialist


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Forum Home > General OW-01 Discussion > Yzf SP ECU, does it worth?

Posts: 11

Hi guys,

I have a couple of questions:

I have an YZF with SP engine working with "R" 38 Mikuni carbs and "R" ecu, both 1993 model.

I was wondering if it is worthy to look for an SP ecu (and harness), to replace the R ecu.

The SP should have a more aggressive ignition map, right?

The bike is for track and races only.

Should I notice a power increase with the SP ecu?

The carbs installed now haven't a TPS to connect to the SP ecu, could it be a problem right?

I know I should find the FCR carbs, but no way.. so should I find out at least newer (and quite rare) carbs with TPS (1996-98)?

Would this effort be worthy in terms of power gain?


September 19, 2017 at 10:43 PM Flag Quote & Reply

Posts: 64

The YZF750 SP CDI has the highest advance of any Yamaha CDI I have seen.  (I have never seen a map for the OW01) so may be higher.  The YZF750 SP advances up to 70 degrees in some places.

I think the last of the YZF750's had a tps. 

I know a guy who built a YZF (jason on here)  full kit racebike and it was maped at 12 degrees at about 1200 rpm up to 45 degrees flat throughout the rpm range.  It was a 850 engine, but made 145 rwhp with starter curcuit still in.

The only difference between the sp Motors, and the R is the close-ratio gearbox in the SP (same box as OW) So you can go either way.

September 20, 2017 at 1:48 AM Flag Quote & Reply

Posts: 11

Thanks Ralph :)

The thunderace carbs should be the same YZF late-years mikuni with TPS. I think that could be a good option after swapping jets, springs, etc.

About the SP advance, it reaches 70degrees but at closed TPS values only...

At full gas the sp advances similar to the R, around 38 degrees, and becomes even lower at 7000 and 11000 where the R reaches 45 and the SP still stays around 38.

Here is the SP ignition graph:

An here is the R one:

Anyway, I think I'm gonna try the SP ecu on the dyno and compare with the R one.

About the 850 engine, I'd like to do it too, but how long could be its track-life?

I'm gonna use it on track all time.. Should I worry about reinforced connecting rods and look after bearings each 5000km?

September 20, 2017 at 6:55 AM Flag Quote & Reply

Posts: 10

I extracted several ignition maps from the TCIs to have a good starting point for the ignitech. Here is a comparison at WOT unrestricted:

The SP map only advances to 70° BTDC at closed throttle as lean mixture with quite a decent amount of exhaust gases at no load burns slow. If you go for 70° at WOT with lot of fresh, rich mixture your engine will eat the bearings.


October 19, 2017 at 2:09 PM Flag Quote & Reply

Posts: 10

Would love to read from a kit ignitor, but couldnt find some...

October 19, 2017 at 2:17 PM Flag Quote & Reply

Jay B.
Posts: 20


I have most all YZF750 and ow01 cdi's.  Are you able to get the ignition curves and information off of them?


Jason B.

October 19, 2017 at 8:23 PM Flag Quote & Reply

Posts: 10

Yes, the device i programmed imitates the pickup signal in 125rpm steps (7 small, 1 big hole pattern used from ow01 - fzr 1000 - yzf 750 - thunderace crankshafts), it also simulates a TPS signal in 50 steps from 0-5000 mVolts and you can select gears, restriction and exup servo dis/connected. Basically everything that can occur in real driving. It records servo and TPS voltage, dwell (coil on), spark (coil off) - after that some work in excel to visualise the data.

Opening the case is not necessary and is a dead end as it is a old 1MHz µC - no hardware tools for that. Maybe in a museum.

What you get from the older non TPS TCIs is one chart for ignition and exup, for the TPS models you get a 3D map for exup voltage and ignition advance. The derestricted units got some retard at high rpms compared to derestricted units. Exup servo missing means usually rpm limit at 4K to get home. Exept my OW01 3PK-00 unit, it does not seem to care if servo is connected or not.

I already covered a lot of different models, only really interested in a YEC TCI.

The 95/96' TCI 82305-10/11 units got a slighly more advance at WOT than the 93/94' units w/o TCI. 38° vs 35° BTDC. The TCI units go up to 66°BTDC at TPS < 15%, but at already 25-30% we are close to WOT values with little decrese towards WOT.

Performance in terms of WOT advance: OW01>SP>95/96>93/94, but only 93/94 come without TPS.

October 20, 2017 at 12:23 PM Flag Quote & Reply

Posts: 11
Hi there I finally run the yzf on dyno with the '93 R cdi without tps and the SP cdi with and without tps. Surprisingly, I found a better curve at top end with the R cdi without tps. The SP ecu gains power in midrange, from 6k to 9k, same hp at 10500 but then it starts losing power after 11k rpm. Finally it losses around 7hp at 13k. The tps reading seems strange because moving the tps from end to end only affects the idl, but the full throttle power curve is the same indipendently from the tps position. Even disconnecting it I got the same curve. I think it should affect the ignition timing. Only the idle seems affected, at least suggesting the ecu is really reading the tps, at least at idle. I haven't tried yet what happens at 50% throttle (f.i). I haven't mentioned the engine is oem and healthy, full exhaust line, carbs are 38 mikuni 96 R model with a rejetted dynojet kit, oem airbox with enlarged entry. The afr plot was pretty same in all tests. However, right now it seems I'm gonna use the R cdi for races. It looks so strange to me having lost power at the top end with the sp ecu. I'd like to try the last easy option: the '96 R cdi with tps plugged. Any idea/seggestion for the disappointing sp ecu behaviour will be very appreciated. Cheers
December 12, 2018 at 11:27 PM Flag Quote & Reply

Posts: 159

Hard to compare power curves, I think, when you're not using FCR carbs like the SP.

Might be wrong.

Are you running a standard motor?


December 17, 2018 at 11:16 AM Flag Quote & Reply

Posts: 11

Hi guys,

here is the comparison on dyno between the 93 SP and the 96 R ECUs, both with TPS:


The engine is the same for both tests, equipped with Mikuni carbs.

The SP ECU gives much more power than the R between 8000k and 11000 rpm, but after this point the power drops abnormally.

Except for the lower limiter, it is impossible that the R 96 ECU is better at high revs than the SP one!

What can be wrong with the SP ECU to make the power drop that way after 11k???

Maybe for using mikuni carbs instead of FCR? The (awful) AFR seems not the problem to explain such behaviour...

I would really like to find out how to make the SP revs well till 13k.

Apart from this, I've just realized that the 96 ECU harness has a plug for gear sensor, which lacks in this 93 engine, so it was unplugged...

According to the service manual, the neutral, 2nd and 3rd gear send a ground to  the ECU when selected.

I suppose this is to use a different (retarded) ignition map.

I'll try to ground it and report back the dyno result ;)

March 1, 2019 at 9:16 PM Flag Quote & Reply

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