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A question about alpha-n tuning .

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I have a wee question about alpha-n tuning .

The engine I have built for my old Honda has rather large ( for the street ) cams with plenty of lift/duration/overlap and itbs to boot.

I keep getting told that a tps based tune is pretty much the only way i'll get it to work .

The itbs I have are black top 4age items and have 4 vac runners to a common port .

I realised that I wont have great vacuum at idle with the large cams and that a slight opening of the throttles will result in a large and rather quick change of vacuum at the port .

Surely the vacuum would stabilse reasonably quickly and give a useable signal at low to middling throttle positions at normal cruising engine speeds .

Can I use map as a reference for cruise up to say 40-50% throttle and alpha-n above that throttle position , or am I stuck using alpha-n and just leave the vac port on the map sensor open and use it for baro correction ?

For got to say , the map sensor I have is the gm 1.05 bar absolute 0-5v motorsport item and I will be running a link g4+ ecu .

Any one had experience with engines like mine or tried some thing similar .

Any help/advise would be very much appreciated

You have literally just missed a live webinar covering this topic, I'm sure Ben will have it a available in the archives soon to watch

Yeah chris250 , I just saw the notification in my emails.

I will be watching as soon as its in the archives

My Individual runner system on a Big Block Ford runs great using a Performance Electronics ECU and Alpha-N. Their system allows the use of MAP compensation as a part of their Alpha-N settings. You get the best of both worlds.

Paul

I think you are not going to have any problem to tune your engine only on alpha-n mode and the MAP for baro correction.

I tune my 3sge engine with itb s and large cams like that with good results.

Like to see the webinar on alpha-n tuning, solid info like always...

As per the webinar, with itb's alpha-n is your only option. You'll simply have no resolution in your fuel if you use MAP and it will be impossible to maintain your target AFR as you open the TPS.

Maintaining MAP as an input to the ECU is still valuable as this can keep the AFR accurate as MAP varies at a fixed TPS. For example as you go up or down a hill at a fixed TPS and rpm, you'll see the MAP signal vary a little. If the ECU isn't compensating for MAP in the background fuel calculation, this will see the engine move slightly rich/lean as the MAP moves around.