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TPS/MAP load sensing

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I have a supercharged corvette z06 with a haltech 2500. Some very reputable tuners led me on to the idea of using tps as a load source. They said they preferred it to using map even in a boosted application. They did mention that some areas would need a correction to work effecitvely but they said that the pressure from boost would be figured in the ve calculation anyway. I set up my tuning this way and have begun to tune the car. I noticed I no longer needed the transient throttle map and that the car was much more responsive. Before I push it very hard and tune the high areas of the MAP is there anything I should be aware of in terms of the corrections needed? Am I wasting my time and should just go back to MAP load sensing? I really like how it has worked thus far and would like to keep using it. Thanks in advance for any advice!

There are some advantages to using TPS as a load input on a turbo or supercharged car and in fact our Toyota 86 is set up this way. Properly tuned, I don't see any real advantage in terms of transient response in comparison to a MAP based load input though. The main benefit is really more to do with maintaining a consistent AFR at part throttle when you're in boost.

If you're using a MAP based load input on a turbo car for example, it's possible to achieve let's say 20 psi at 5000 rpm and 100% throttle. If we close the throttle slowly we may find that at 60% TPS we still see 20 psi boost despite the engine VE being reduced by the partially closed throttle - The end result is that we see the AFR move richer than target at these part throttle settings since the ECU is basing fuelling solely on MAP.

One thing you need to watch on a turbocharged car is that often a 4D compensation map will be required to maintain consistent AFR as you push the turbo harder and turbine inlet pressure increases. I'd suspect this is much less of a concern on a supercharged engine though.

Very interesting, I suppose the advantages I felt I have seen may have a lot to do with how optimized my tune is running map as a load access. The odd thing about transient response using tps in the haltech was that it no longer accessed the transient throttle tuning maps. I wasn't really sure how to tune these and have had mixed results but with tps as a load access it seemed to transition smoother without touching the transient throttle maps. Particularly coming out of fuel cut the car surges a lot more and doesn't move to a richer afr quick enough, the car was much more pleasant to drive operating with a tps load axis. I suppose this has a lot to do with my transient throttle tuning? How should I go about tuning those maps? If I switch back to tps how should I go about making the compensations in boost? What i noticed running tps was that as i would increase the throttle loading up the car the boost area of the map was unpredictable and would be different each time I hit the zones again after already having tuned them. The interesting thing with the blower combination is as soon as the bov close at 3 inhg it moves rather quickly to the maximum boost it can produce at that rpm. It seems to make about the same boost from as low as 50% throttle to 100%. Thanks again andre for all the advice!

On turbo cars with ITB's this is really the only way to go. How I go about it is to open the wastegate. Then tune the VE map up to 100% TPS, and max RPM with the minimum boost possible. Then put the gate spring back in, or hook the actuator back up. I've only seen it go rich when it sees more boost, as the increased exhaust pressure "chokes" the VE.

In the 2500, go to Setup-Engine-Fuel, and enable the MAP correction table (your 4D). This table is zeroed out. When the boost goes up, and it goes richer (or leaner), at that RPM and MAP, simply correct the fuel to get the AFR you want.

There's a webinar in the archives called 4D tuning. Matt from Haltech, and Andre really got me informed on this. It's surprising how so little info is out there surrounding this, but it's a really good way to tune any car.

Hey Matt, provided the fuel model is set up correctly, there's no need to start by opening the wastegate. I simply start at the minimum boost I can achieve on the wastegate spring pressure and tune from there. The basis of the fuel model is that as we double manifold pressure, we need to double the fuel mass delivered to maintain a consistent AFR. This tends to work pretty well provided we're operating the turbo somewhere around it's peak efficiency. As we start pushing the turbo very hard and EMAP climbs, the fuelling will tend to go rich and this needs to be compensated with a 4D table.

thanks for the advice guys, i had no idea there was a webinar on this topic and I'm definitely going to check that out now. Although it sounds like the issue in which the turbo efficiency effects the ve and causes a rich condition would have no real relation to my situation with a supercharger. Im starting to think there may be another issue with the car or with the haltech itself. The more i think about it after hearing from you guys it seems as though if I tune with tps I shouldn't really even need a map correction and my afr should remain consistent once tuned correctly. This may get a little off topic of the original post but with the variation and sometimes unreliable nature of widebands is it likely some of my issues could actually be false readings from one or both of my widebands? Im thinking there is also a chance I have some issues with how I configured the software. Im not at my tuning computer at the moment but Im gonna post some of my tuning files and logs so you guys can take a quick look.

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