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Discussion Starter #1
I had an issue at a recent track event recently where at the end of 2 out of the 3 races the car suffered froma severe lack of throttle response at the lower end of the rev range. Once it eventually picked up it would happily rev to the limiter.

Once the car stood switched off for a while it would be fine again.

It was a hot day so the car ran hotter than usual (110 degrees versus the usual 100 degrees water temp), but I don't know if it would cause a temporary response issue?

I have run diagnostics using Multiecuscan and there were no new error codes.

I haven't been able to replicate the issue off the track, so not sure where to go next.

Any ideas? Throttle body, air intake, fuel pump?

Cheers

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I'll take a guess at a heat soak issue when only happens when the engine gets to the high temperatures experienced on a track.

Take diagnostic gear to track day and check inlet air temperature but it is possible the fuel gets too hot (closed throttle, low rpm).
The fire prevention system means fuel does not return to the tank and moves slower and absorbs more heat in certain conditions.
 

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Discussion Starter #3 (Edited)
Thanks Fruity, that's useful information. Do you perhaps know where I could find the range of normal (min and max) values for the various ecu readings like intake air temp, air volume, etc?

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Hi Jules. I'm not sure which engine you have but a I'm guessing it's a TS.
A 1.6 should be able to produce close to 400kg/hr,
a 1.8 close to 410kg/hr
and a 2.0 420kg/hr.

Be aware that not all diagnostic equipment seem to register above 408kg/hr or it may be a programmed maximum value for certain engines.

My JTS returns 460kg/hr which is very exceptional as Stephan of Squadra Tuning tells me he has never seen more than 440kg/hr.

All the values max out at the point of maximum power which is 6000-6400rpm. At this point, the throttle must be fully open. I found out doing left foot braking for slow acceleration, uphill and into wind help make it easier to capture an accurate maximum value. Doing this in 2nd gear means no excess speed must be attained.

Inlet air temperatures are a little higher than ambient but reduce closer to ambient with a warm rather than very hot engine but hopefully you won't see more than about 40 degrees. The temperature is greater with a stationary car or only slightly open throttle as opposed to a wide open throttle. With an open throttle, the air goes through the induction system quicker so is less prone to being heated by engine bay heat soak. Also, think about wind chill phenomenon.
 

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Discussion Starter #5
Thanks for that. Apologies, should have mentioned that I have the CF2 2.5V6 with stock air intake and cooling system.

When I tried to replicate the issue I ran the car at high revs while stationary to get the temps up, but even at 112 degrees water temp and 50 degrees intake temp it didn't want to produce the isssue.

I'll flush the coolant, clean the throttle body (carefully) and hope for the best.

Niw I just need to find a way to safely log the ecu readings while on the race track - I'm guessing the ecu itself doesn't store any data?

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Discussion Starter #6
Hi Jules. I'm not sure which engine you have but a I'm guessing it's a TS.
A 1.6 should be able to produce close to 400kg/hr,
a 1.8 close to 410kg/hr
and a 2.0 420kg/hr.

Be aware that not all diagnostic equipment seem to register above 408kg/hr or it may be a programmed maximum value for certain engines.

My JTS returns 460kg/hr which is very exceptional as Stephan of Squadra Tuning tells me he has never seen more than 440kg/hr.
As a reference, here are the max values for my 2.5V6 during the test. As mentioned, the car was stationary on a hot day, so not sure if the figures are an accurate reflection of what would happen while driving on a track (no airflow)

Intake air temp: 59.8 C
Engine temp: 114.5 C
Air quantity: 567.9 kg/hr

I also noted a parameter called Evaporation Canister Control which made me think of your fuel comment. That parameter maxed out at 100% a few times.

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The ECU won't store data but the diagnostic software should have some sort of ability but MES isn't really meant for race car data logging so it can't store enough to be as useful as perhaps you may like it to be.

Your data looks ok. Obviously the MAF airflow is good but the temperature is high but this is to be expected. Perhaps the car was being used in high ambient temperatures so there is not necessarily an IAT issue with the MAF. V6 engines produce a lot of under bonnet heat- more so than an inline of straight engine due to the greater surface area of hot engine casings.

The fuel evaporation valve will be open as the car will be consuming a lot of fuel at the time, it is hot etc so I'd expect this to be the case. It goes back to perhaps the fuel becoming hot around the fuel rail if a sensor isn't getting too hot and starting to produce a bad signal. Even then, I'd have a good look at the wiring and terminals first as a thorough clean up of that only costs time and is very good preventative maintenance anyway.

As the coolant temperature seems high (I realise the car was stationary), are all the radiator fins (and AC condenser fins) clean and undamaged? The fins do tend to suffer minor damage in the course of hitting insects and small stones over their lifetime an this can have quite an impact on the air flow through the radiator. Whenever I have bits off for access, I spend quite a bit of time cleaning the fins and straightening bent ones as even the JTS radiator with an AC condenser in front of it doesn't cool as convincingly as I'd like it to. In this respect, the cars without AC fair quite a bit better even when the AC isn't being used.

Other people with more Busso experience may be able to give a more definitive answer but at present, that's about as much as I can suggest.
 

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Discussion Starter #8
As the coolant temperature seems high (I realise the car was stationary), are all the radiator fins (and AC condenser fins) clean and undamaged? The fins do tend to suffer minor damage in the course of hitting insects and small stones over their lifetime an this can have quite an impact on the air flow through the radiator. Whenever I have bits off for access, I spend quite a bit of time cleaning the fins and straightening bent ones as even the JTS radiator with an AC condenser in front of it doesn't cool as convincingly as I'd like it to. In this respect, the cars without AC fair quite a bit better even when the AC isn't being used.
I'll add checking and cleaning the various sensor connectors to my list of maintenance activities.

I'm not sure about the age of the radiator, but judging by the state of the car when i bought it as a road car 3 years ago, I would say it's pretty old. I'll remove the bumber and inspect it a bit closer.

I'm looking to remove the non operational a/c (all components in the engine bay) anyways, so hopefully that will help with cooling too.

Thanks again for taking the time and for your advice.


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That's ok. When choosing a radiator, if needed, be aware some aftermarket types use different dimensions for core thickness which may be ok in a TS but not so good for a V6 being used on track. Look at www.autodoc.co.uk to see what I mean.
 
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