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Intercooling -v- ECU

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Have been researching intercooling and other mods for the V8 for a while. So far I have some up with the following that relate to what the ECU and the standard installation allow:

 

i) the primary ECU defense is via the ignition timing which backs off at IATs over 50°C.

ii) the IAT sensor is mounted right on the turbo outlet rather than somewhere sensible like the common throttle bodies. Hence long thermal lag effects.

iii) the ECU defense against overboost is overfuelling, so there is little point in going over 0,7 bar stock boost.

iv) even if you go over stock boost levels, the ECU will also back off the wastegates duty cycle at IATs over 50°C

v) on a typical day at 20°C you will only get 0,4 bar before the IAT will exceed the ECU defence limits.

vi) even stock, you are unlikely to see 0,7 bar boost in other than transient conditions (or very cold days)

 

Does that sum up the reality that people have found?

 

Logically the only significant avenue to explore is controlling the IAT?

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Your summary is fairly accurate, however the control logic is somewhat more complex and interelated between IAT and MAP, with both timing advance and wastegate duty cycle being control elements. Your conclusion is correct, in that, to preserve all the boost designed into the engine, control of IAT must be maintained below 50* C. Additionally cranking up the boost via an external device will only lead to enriched fuel mixtures.  Intercooling is a complicated project due to the packaging of the Esprit. Here is the approach I followed, http://www.thelotusforums.com/forums/topic/33622-intercooler-project-finally-finished/

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Wayne, think you can put those in the right folders an do a 're-play' ..right ?

 

..shout be a good verification on what the ECM does without chargecooling

 

(no external bost controler, no water injection ..just some other capsules, and now also different injector setup on this)

 

IAT on first *log without rpm should be ambient temperature in °C, just for comparision

 

http://www.imagenetz.de/f17a1b178/SCAN50.DAT.html

http://www.imagenetz.de/fcd7910be/SCAN52.DAT.html

http://www.imagenetz.de/f89cd7028/scan.num.html

http://www.imagenetz.de/f519ba3f0/SCAN50.log.html

http://www.imagenetz.de/fc009891e/SCAN52.log.html

http://www.imagenetz.de/f5759be50/scan.vin.html

 

 

..as for the repositioning of the IAT, those cars without EGR system have a unused port there on the intake .this could be used for it, at least this was a thought I hade sometimes in the past.

 

..in the second run (*log52) the ride was a little more forced, as you can see by engine-intake (IAT) of nearly constant 50°C+ and peaks to over 60°C   ..with 0.8bar of boost from 60-100% TP

Edited by Günter

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Wayne, your installation is fabulous! But I think I will go with a lower profile water injection set up.

The one from PUK looks interesting, especially as it is boost programmable for both start and full. However they have 100ml/m injectors which may be a little too much? I would have thought that half that would be enough?

 

Then there is the question of % octane booster to add to the mix....

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simply use E85 ..or ethanol in the bottle, like to use for the screenwasher.

 

if you mix this up with your water injection it should work to. The water-injection sets are available in various tuning shops, there is no need to pay PUK/R&B prices me thinks ?

 

If Wayne could do a replay of those vehicle-explorer log files (think he has the software to..) ..maybe you can see how the ignition timing does change under boost -as I can only see the small graphic-plot on the screen here, if I choose the timing.

 

an overall chart of the whole run in *doc/*pdf would be good to compare with his chargecooled runs

Edited by Günter

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Gunter, I reviewed two files scan50 and scan52. General comment: you need to select fewer PIDs to record and up the scan rate. The ECU will still respond when scan interval is cranked up to "hyper" level.  Your sucessive sample rate of 5.11 seconds will miss the short tern peaks.

 

Scan50 shows a maximum of 138* F at 629.5 seconds after a pull to 4327 RPM and a TPS of 100% and a WDCP of 42.2 %. The IAT is starting to climb but the next sample TPS was back to 0, so no time for heat to build. Yes the timing falls to 6* at that point which is correct, all to protect the engine while under boost when an intercooler is not used. 6* is about the minimum the advance falls to under full boost (WDCP about 62% maximum for all factory ECUs.

 

Scan52 shows two IAT peaks of 145* F at 277.81 and 283.03 seconds after a pull to 4575 RPM and a TPS of 100% and a WDCP of only 32.8 % timing fell to 7* again just about correct.

 

Information from Lotus engineers tell me that as long as IAT is below 120* F it will not retard timing. The data clearly shows that the boost levels (MAP) are impacting the timing, which is correct. You can infer the IAT is begining to impact WDCP in scan52 as at time stamp 272.65 seconds IAT is up to 145* F and WDCP is only 38.7%.

 

I would not draw any serious conclusions from this data as there are some many PIDs being recorded and the sample rate is set so low that there is a major amount of time skew between samples.

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it was at least just a test run to prove that the computer still works on the interface -and you are right that there are many 'not usefull' PID

 

..but I hope it is still good enough for an overview for others. As said, with this style of driving/ power demands the ECM can handle it, and I don't see the need for more power (or 'unrestricted power' , in terms of ECM irgintion timing changes) for me so far

 

we could say that this car is still within the factory limits ..so if someone wants to see what happens with this kind of boost level it should be of good use for those guys.

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With the data I can find for the T25 turbo, it seems that the IAT rise is around 5°C / psi boost. (If anyone has a known figure for the adiabatic efficiency that would help?)

Therefore under themal equilibrium the ECU is not going to allow max power if the ambient is over 0°C. Most injector pumps are simply controlled by boost pressure with programmable start and full on levels whereas it would be much better if it was combined with ambient temperature. There would be little point in even running the injectors at all these winter mornings as it feels like the car has reverted to full-on animal mode :driving:

So the winter project is going to be to design a pulse width modulated pump controller with ambient temp and boost level inputs.

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as you say - like an Animal ..a hughe one  !

 

..I'm actually on my winter tires, running great ..but notable wheelspin and 'tailhappy' in 1/2/3 as soon as 3000rpm is on the dial :D

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