Multiple map facility based on throttle angles for RB26 ecus?

[Chris Wilson]

I am deciding on an ecu for a fairly radical, MAP sensored RB26

Skyline engine. Having 6 throttle bodies close to the ports I am told

that having the ability to run multiple maps via throttle angle

correction is a Godsend. AFAIK only the Pectel t6 has this ability, is

that so, and how much of an advantage is it to have this facility? I

don't think any Haltech ecus, or even an M800 Motec allow this, do they?

Cams are 280 degree with 11 mm lift, big single turbo, stock plenum, 50

mm throttle bodies (bored out stockers with DCOE plates in them).

Thanks.

[RB30-POWER]

Very hard to tune engines with individual t/bodys and big cams with a Speed Density Type Engine Management arrangement.

One reason why most GTR still use AFM (usually upgraded but)

Even though there is none/very little manifold vac/erattic vac for the map sensor to measure accurately the AFM is able to measure the actual air entering the engine and report that output to the ECU very accurately.

If your not looking at running AFM arrangement, which it sounds like your not.

Then much as you said. Its probally best to tune small throttle openings or non boost pressure throttle openings against throttle position, then change to the map sensor as the motor produces boost or positive pressure, which can be measured and map against sucessfully.

Can't say im familiar with the Pectel T6 managment system, but i find it hard to beleive that the Motec would not be capable of doing what you want to do.

Motec are GOD (You will pay though)

[Chris Wilson]

I was going to run my motec M800, but those that have mapped boosted engines with more than stock duration cams and multiple throttle bodies have found just what you stae. pectel designed the T6 software to counter exactly this, and those that are familiar with it in this scenario, indeed he who wrote the software, feel it is ideal to have no MAF sensor restriction, and yet overcome the low and erratic vac signal from such multiple throttle body systems. AFAIK even the latest Motec M800 software won't accomodate this type of offset mapping.

[StockyMcStock]

there are quite a number of ways around MAF "restrictions" you know..... things like using twin Q45 AFM's on the intake pipe for example. you can't tell me that twin 3 inch ID intake pipes (and hence pod filters) is going to cause a restriction which can be seriously measured?

[Zoltarc]

I use a Haltech E11v2 ECU on a 3S-GE with quad throttle bodies using a MAP sensor for load sensing.

This causes two main problems. "Bouncing", oscillations or fluctuation's in the map signal, which is very obvious at idle and low dynamic range of the MAP sensor.

To cure this problem firstly a vacuum tank was installed in the MAP sensor line to dampen the bouncing as much as possible. Then I designed a small circuit that would use a 'capture-and-hold' IC that samples the MAP sensor when the piston is creating maximum vacuum. That signal was then passed through a few signal conditioning op amps to try and 'expand' the signal to get back some dynamic range. Although the circuit worked well it was extremely difficult to calibrate.

About a year ago the car changed ECUs to the Haltech E11v2. There is a useful software function that you can use to calibrate the MAP sensor where you say X manifold pressure is equal to Y volts. You can then scale your actual MAP sensor range accordingly to get your dynamic range back. This is what my circuit did but is now managed via the E11v2.

While I believe the E11v2 can't use multiple MAP sensors it can use TPS_MAPXBARCORR where the TPS is the main load sensor and then references the MAP sensor using a 3D table for extra fuel correction. This is the opposite of what the Pectel system has.

However in theory you could interface multiple MAP sensors to any ECU. If you arranged 1 MAP sensor per cylinder and then used a PIC micro controller that was aware of TDC for #1 or was interfaced to the timing pickup, you could sample each MAP sensor when the piston was creating the most vacuum and then output that signal to the ECU.

A simpler arrangement could be sample and average. Use two or three MAP sensors, add the signals together and divide by the number of sensors. Then output that to the ECU.

[Gav]

Interesting thread

Anyone know how the D-Jetro PFC deals with this phenomenon/problem (if at all?)

[RPMGTR]

A Motec tuned using throttleposition/map for fuel, will run beautifully. We have used them on 6 throttle RB's with cams up to 304deg and drivability is still remarkably good. May take a bit of tuning but can be done...