question for all the tuners

[TonyTwoTribes]

My Bathurst S is running the mild walky cam, low miles 14k. When cold it barks into life, but sometimes starting when hot it starts but kinda slow, like phut phut brummm but not with the same vroom as when cold. - hope that makes sense?. Goes great however. My last Bathurst S never did this but never had the cam mod. maybe normal, any ideas?

[stevieturbo]

Most likely a tuning issue. Assuming of course it isnt just an unrelated fault.

[Z0m81e]

I have a mild monkfish cam and mine sometimes isn't keen to start when its hot either. It's a bit better since they adjusted the tune but its still not as good as when its cold.

[TonyTwoTribes]

Thanks I will talk to walkinshaw next week. Probably a compromise due to the cam.

[Mud_]

B4343 ('Startup Friction Airflow Correction') is the standard tweak on LS1B with a new cam:

"Correction to idle airflow on startup to overcome initial starting friction and cold/stiff engine components."

Mine's about 3g/sec higher than standard above about 80'C. I'd be surprised if you didn't have a similar modifier. It's actually about 2-3g/sec higher everywhere, I think most people use the same values (which are decayed out quickly).

[Z0m81e]

Mud_ said:

B4343 ('Startup Friction Airflow Correction') is the standard tweak on LS1B with a new cam:

"Correction to idle airflow on startup to overcome initial starting friction and cold/stiff engine components."

Mine's about 3g/sec higher than standard above about 80'C. I'd be surprised if you didn't have a similar modifier. It's actually about 2-3g/sec higher everywhere, I think most people use the same values (which are decayed out quickly).

Sounds likely mine (automatic) used to also stall very shortly after starting if I was e.g. driving round a car park and pulled up, which is now fixed.

[Mud_]

Z0m81e said:

Sounds likely mine (automatic) used to also stall very shortly after starting if I was e.g. driving round a car park and pulled up, which is now fixed.

Could be for all I know - getting the return to idle right under all conditions can be a bit hit and miss. Here and here are some reading on idle - the startup friction bit is in the first link.

[MilkyV6]

Mine does the same, sometimes starts from hot at about 400 rpm then after about a second idles normally- I have no tune (unless the radio is on haha)

[Janosh]

TonyTwoTribes said:

My Bathurst S is running the mild walky cam, low miles 14k. When cold it barks into life, but sometimes starting when hot it starts but kinda slow, like phut phut brummm but not with the same vroom as when cold. - hope that makes sense?. Goes great however.

Mine was the same albeit on occasion it wouldn't start on the first turn of the key.

Z0m81e said:

I have a mild monkfish cam and mine sometimes isn't keen to start when its hot either.

+1 although it's much better since I had a new starter motor fitted

Mud_ said:

B4343 ('Startup Friction Airflow Correction') is the standard tweak on LS1B with a new cam:

"Correction to idle airflow on startup to overcome initial starting friction and cold/stiff engine components."

Mine's about 3g/sec higher than standard above about 80'C. I'd be surprised if you didn't have a similar modifier. It's actually about 2-3g/sec higher everywhere, I think most people use the same values (which are decayed out quickly).

I assume that the known tuners adjust this value when fitting cams?

[ringram]

Janosh said:

I assume that the known tuners adjust this value when fitting cams?

You would be surprised at who does what.
And not always (often) in a good way.

[Mud_]

Janosh said:

I assume that the known tuners adjust this value when fitting cams?

I don't know who does what, but looking back through my tunes my values that particular modifier was tweaked up and down a bit to get it right...this is just one aspect of getting the idle right, and a tuner has a limited time to fiddle with this sort of thing (and limited cold starts, etc.), so it's easier to bump up the idle or focus on standard modification packages.

[ringram]

Yep, spoke to Greg Banish at PRI around a few topics and he was quite clear that to do a tune properly you are looking at days of time to do it properly, if not weeks.
So adjust your expectations accordingly for tunes that are done in hours. Hence my preference for helping people onto the path to the promised land by getting them started with their own tune setup and a baseline.

[TonyTwoTribes]

Thanks for all the info. Idle is definitely tweaked so not too lumpy. Guess it is a compromise between street drivability and more oomph. probably about right on mine reading this thread.

[rich24v]

ringram said:

Yep, spoke to Greg Banish at PRI around a few topics and he was quite clear that to do a tune properly you are looking at days of time to do it properly, if not weeks.

Amen to that !!

[ringram]

TonyTwoTribes said:

Thanks for all the info. Idle is definitely tweaked so not too lumpy. Guess it is a compromise between street drivability and more oomph. probably about right on mine reading this thread.

Nope its a compromise between time and driveability.

More time = Good power AND good driveability.

Less time = Ok power and ok (if you are lucky) driveability.

DIY FTW IMO

[TonyTwoTribes]

Best tuners?.

[ringram]

General Motors, Ford, Dodge

[MyM8V8]

ringram said:

General Motors, Ford, Dodge

Amen to that!

[TonyTwoTribes]

LMFHO!