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SD vs Alpha-N
Nitrogeno25 - 6/6/11 at 05:18 AM

Why is it recommended to run SD for engine load insted of Alpha-N?

I understand that when using ITBs, the vaccum signal is not useful and thats the case where Alpha-N cames to play. But is ther any benefit of one over the other?

Thank you very much!

rf900rush - 6/6/11 at 07:43 AM

I did have this problem on my RF900R bike engine using MS.
High performance engines like bikes do have very poor vacuums. Hence the Aplpha-N.

Have a look at MS-Extra system. This also has a Hybrid version combiine both Map and TPS.




LINK to MS-EXTRA

Martin

matt_gsxr - 6/6/11 at 08:48 AM

The ITB mode may be the same as the hybrid described above.

The problem with SD on TB's is that you get quite a lot of MAP noise (improved on later versions of MS, and can be dealt with using damping [fuel filter and small hose restriction]) at low RPM. At wide throttle openings the MAP goes to atmospheric before WOT is achieved and it turns out that airflow is not always well represented by the MAP.

The problem with TPS (alpha-N) is that you get big air flow changes for small changes in throttle position, which can be difficult to dial in, and can be sensitive to slack in the TPS and imbalance of the different bodies. The tiny throttle openings are reflected quite well in the MAP, which makes MAP good at low throttle openings (assuming a stable MAP can be obtained).


MS offers a few options beyond the pure SD and pure Alpha-N:
Blended, which uses a complete SD table and a complete alpha-N table and multiplies or adds them. This allows a lot of flexibility but it is more difficult to tune, as the autotune features can deal with either table, but not both at once. I am running this way and you have to tune one for a bit and then the other. Doesn't seem too bad though.

ITB mode. This uses MAP at low TPS, and TPS at higher TPS. You get the best of both worlds, and the automated tuning tools can deal with this.


What engine are you mapping?

Matt

[Edited on 6/6/11 by matt_gsxr]

[Edited on 6/6/11 by matt_gsxr]

Nitrogeno25 - 6/6/11 at 02:04 PM

quote:
Originally posted by matt_gsxr
The ITB mode may be the same as the hybrid described above.

The problem with SD on TB's is that you get quite a lot of MAP noise (improved on later versions of MS, and can be dealt with using damping [fuel filter and small hose restriction]) at low RPM. At wide throttle openings the MAP goes to atmospheric before WOT is achieved and it turns out that airflow is not always well represented by the MAP.

The problem with TPS (alpha-N) is that you get big air flow changes for small changes in throttle position, which can be difficult to dial in, and can be sensitive to slack in the TPS and imbalance of the different bodies. The tiny throttle openings are reflected quite well in the MAP, which makes MAP good at low throttle openings (assuming a stable MAP can be obtained).


MS offers a few options beyond the pure SD and pure Alpha-N:
Blended, which uses a complete SD table and a complete alpha-N table and multiplies or adds them. This allows a lot of flexibility but it is more difficult to tune, as the autotune features can deal with either table, but not both at once. I am running this way and you have to tune one for a bit and then the other. Doesn't seem too bad though.

ITB mode. This uses MAP at low TPS, and TPS at higher TPS. You get the best of both worlds, and the automated tuning tools can deal with this.


What engine are you mapping?

Matt

[Edited on 6/6/11 by matt_gsxr]

[Edited on 6/6/11 by matt_gsxr]


2.0 Duratec, now with 45 Jenvey TBs. No vaccum port provided in the Jenveys, that's why I plan pure alpha-n at first!

matt_gsxr - 6/6/11 at 09:26 PM

Alpha-N should work nicely.

I've heard that Jenveys are better at the low throttle openings than the motorcycle equivalent. I have no direct experience of this, only what I have read.

Matt