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Itb with turbo - tuning strategy

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Hi to everybody

I am just building my engine but I want to get problems sorted out.

I am running am BMW s38 engine with individual throttle bodies for each runner combined with a turbo.

Engine management is a v88

I normally take the map pressure as the load signal.

On this engine with its, the map signal behind the throttles is very rough and not usable for application.

So I rather use the 4d map with the tps as load for the base map and then map for the correction.

But how do I start: run the base map with no boost at all ( disconnect turbo?) ???

And then do the correction with map signal and the 4d table? In first row has to be 100kpa???

I think fuel will not be the problem, but how I gonna handle the ignition since with more boost I have to reduce the ignition...

If anyone has an example or a good hint how to do it would be lovely!

Thanks

Phil

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I run ITB's on my naturally aspireated Neon. Even with 2 vacum canisters the map dances between 70 kpas and 75 kpas at idle with throttles closed.

I'm going to change from a Map axis to a TPS axis When I get it running again ( presently found some mechanical problems)

Please post what you have done.

Thanks

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I prefer using the fuel table setup as TPS. Disconnect boost and tune for fuel up to 100% TPS.

Setup ignition table as MGP. You may have to setup a 4D table as well for ignition with TPS to compensate (add ignition) for low load/low tps as normally you have very little vacum with ITB engines.

Setup a 4D fuel table with MGP and then connect boost and tune boost cells. Keep the upper cells at 100.

Thats the way I feel works good, but there may be different ways to do it.

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Here´s one way:

"You do not have to make it all that complicated as the Vipec ECU have a very powerful method of mapping this type of engine. You have the fuel table axis set to TPS and the AFR correction turned on. You then map the engine on TPS and the ECU will lookup the target AFR table to know how to change injector time based on manifold pressure changes.

You do not need a 02 sensor or wideband for this to work. It is all done with maths.

You set the fuel table axis to TPS, and then tune based on TPS, and the ECU looks up the AFR table to know how to adjust injector time as the load (manifold pressure) changes. No 4D or 5D tables are needed."

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Hi to all

Are u sure it will work on this engine only using tps as load?

What happens if I run different boost and what about the ignition?

It will make a difference if I run 6000 rpm at 100% with 1 bar or with 2 bar.

This has to be done by a 4d map for sure for ignition?!

ThAnks a lot

I hope this is an interesting topic

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The ECU will need to see boost so you can add compensation if needed.

As the fuel calculation takes in to account MAP it will do some correction automatic. If more is required (usually is) then you use the 4D table to correct the fuel.

Ignition is the same but there is no correction unless you add a 4D table based off MAP or MGP.

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The ECU will need to see boost so you can add compensation if needed.

As the fuel calculation takes in to account MAP it will do some correction automatic. If more is required (usually is) then you use the 4D table to correct the fuel.

Ignition is the same but there is no correction unless you add a 4D table based off MAP or MGP.

Simon,

What´s the point of using 4D table with this kind of set up since the 4D table affects the main fuel table (i.e the numbers in the main fuel table could be changed accordingly?)..?

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The 4D is a trim on top of the main table and it allows trims based on other inputs.

In this case the main table is based on TPS and then the trim would be in MGP giving two load inputs.

This allows for the fact that TPS is not a true load indication but it is need as on multi butterfly applications the MAP signal is not stable.

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Hi Simon

So I was on a good way.

For fuel: do a base map with tps as load with no boost ( bypass the turbo) and then do a correction on map with boost using a 4d table with map as load.

For ignition: this is for me more complicate or dangerous. I could also do a base map with no boost with tps as load. Then do a correction with boost adding a 4d table with map as load. But: in the 4d table has to be a ignition reduction because I cannot run the ignition values of the tps base map when boost is added. So how do I do this while tuning. Adding negative values??

You know someone who tuned this kind of engine? In Sweden a ot of guys are running this setup.

Thanks for all help

Phil

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It is hard to tune the ignition so most don't use the 4D and span the main table off MAP.

As the ignition timing is not changing much in the off boost section of the map. You could then to refine it use the 4D table based on TPS.

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What Simon says works very well. You can have ignition only based on MAP/MGP, but you will loose power on low TPS like cruising. Better setup 4D ignition spanned on TPS to add timing on light load. You can have 100 kpa manifold pressure with 100% TPS @ 2000 rpm, but you can also have 100 kpa manifold pressure with say 40% TPS @ 2000 rpm. These two different scenarios, needs different timing even if they have 100 kpa manifold pressure.

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Hi, what Sutkale said in one of the above posts is right. I have tuned quite a few GTR's some with big cams and this works perfectly for me with all happy customers-good power and economy. Start with FUEL MAIN then set LOAD=MAP and OPEN LOOP FUEL TABLE TO ON. Then set up the A/F TARGET TABLE to the A/F you want at the various loads as you normally would. Then set the main fuel table to LOAD=TPS. Then ignition to LOAD=MAP. You may find when on the road you may need some unusally high timing numbers in the 80kpa to 100kpa area for example I have 38 in 100kpa and 41 in 80kpa around 3000rpm but it all works pefectly. The software is so good I run 30psi in our GTR and do not have to alter the fuel table-its so easy to tune on TPS. You will soon learn to trust it-just shake your head and believe.

Cheers, Grant.

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Hi, what Sutkale said in one of the above posts is right. I have tuned quite a few GTR's some with big cams and this works perfectly for me with all happy customers-good power and economy. Start with FUEL MAIN then set LOAD=MAP and OPEN LOOP FUEL TABLE TO ON. Then set up the A/F TARGET TABLE to the A/F you want at the various loads as you normally would. Then set the main fuel table to LOAD=TPS. Then ignition to LOAD=MAP. You may find when on the road you may need some unusally high timing numbers in the 80kpa to 100kpa area for example I have 38 in 100kpa and 41 in 80kpa around 3000rpm but it all works pefectly. The software is so good I run 30psi in our GTR and do not have to alter the fuel table-its so easy to tune on TPS. You will soon learn to trust it-just shake your head and believe.

Cheers, Grant.

Exactly. The main fuel table is pretty damn easy to tune with this set up. Once its done just alter the AFR target table, if you want to change your AFR values.

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Hi

Sorry for my late reply. I am just back from the 24hr nurburgring - unfortunately my car crashed in the morning because of oil and water on the track. At this time we were p3 overall - shit happens.

Now back to topic. Thank you all for your good replys. If someone can send me an example map would be nice to see.

So fuel is clear and ign only over map - where do you get your map signal from? Each runner in one extra volume or just from the intake manifold which would be before the runners?

If I do ignition only over map on this setup, what about the idle?

Thanks again

Phil

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The best map signal will be if you can join all 6 runners in to a common map line back to the map sensor.

If you find you want trim ignition more this is where you start to use the TPS overlay.

The overlay allows you to remove or add timing from the main MAP based table off throttle position.

So you might find you need to add some timing at idle, so in the trim table at 0% TPS and low RPM you can add timing as soon as you increase TPS this area is not active and the timing is removed.

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If anyone has an example map I can look at it would be lovely - just for understanding.

Phil

Are you after the TPS based map? I´ll try to send you one. Just throw me your e-mail address.

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Hi sutkale

Base map to look at will be interesting. Please send to Philipp.mondelaers@gmail.com

As I said, I am not worried about the fuel adjustment, but more about ignition with this kind of setup.

I met this weekend some guys in Norway which are running similar setups. They combined all 6 runners to get a smooth map signal. But I still think I have to use the 4d table for ignition adjustment, or? Doing it just over map and rpm with this itb and turbo will not work? There are a lot of guys running vipec with itb and turbo. Where are they? :)

Good discussion here anyway - helps a lot.

Thanks a lot guys

Phil

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You can have ignition only based on MAP/MGP, but you will loose power on low TPS like cruising. Better setup 4D ignition spanned on TPS to add timing on light load. You can have 100 kpa manifold pressure with 100% TPS @ 2000 rpm, but you can also have 100 kpa manifold pressure with say 40% TPS @ 2000 rpm. These two different scenarios, needs different timing even if they have 100 kpa manifold pressure.

So yes, better setup a 4D ignition table to get more power on light load/low TPS. It will work without 4D ignition, but you will sacrifice power on light loads.

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This is what I meant aswell - I think I will have to use the 4d map.

This is why I started this topic:

How do I start?

base map on RPM vs TPS (no load / with load? deactivate turbo)

4d map over RPM and MAP ( decrease the values of the TPSvsRPM base map??? or is there a better way?

How do I do this - sounds very complicated or lets say hard to do, because you can have 4000 RPM with 60% TPS and 1 bar map , 1.5 bar map 2 bar map...

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Hi, you are making this way more complicated than it needs to be. Just try it like I said instead of talking about it. I have 280 degree cams and I dont have the same vacuum at 40% throttle at 2000rpm and 100% throttle at 2000rpm why should you. Don't forget you can put very fine map points into your maps, your not just stuck with generic points like on most other ecu's. Do you have a manifold supply to the fuel reg. if so use it, if not all the runners between the t/bodys and head may need to be all connected with small fittings and "t" pieces to get an even, although low map reading. The GTR's have a common vacuum source for the fuel reg. which we always use for the map signal as we do on all engines with a manifold signal to the fuel reg. As I said before just trust the Vi-pec-it works. I will send you a map from a GTR.

Cheers, Grant.

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