P38A Sport mode

Rubberknees · Feb 4, 2022

DanClarke said:
TBH I find my P38 is plenty fast enough for me and I have not made much use of "Sport" mode.
A 2 .5 Ton vehicle is never going to win a drag race or win at speeding away from a traffic light, so why bother?
4.6L seems happy enough chugging up hills although I think my injectors have been replaced with watering cans considering the consumption figures.

Same with me. Got the MX5 to go flying round country lanes in

Datatek · Feb 4, 2022

Henry_b said:
Idling in drive the torque is miniscule compared to cruising torque, let alone accelerating torque levels.

Shifting from Drive to Neutral can increase wear in the gearbox solenoid pack and wet clutches. Leaving it in Drive doesn't - it just warms the fluid slightly but well within the parameters which the gearbox cooling features are intended to cope with.

The biggest no no with the HP22 is free revving it in neutral, the hp22's clutch shaft's two O-rings, which let's the pressure towards "A" clutch pack. When the car is run at high rpm in N or park, "A" gets pressured slowly and starts to slide/slip and the trans will grenade.

The manual valve controls the fluid supply for P, R, N and D selector positions. The four solenoid valves operate accordingly to operate shift control, lock-up and shift quality. Solenoid valves MV 1 and MV 2 control the supplies that operate the brake clutches for shift
control. They are also used to prevent accidental engagement of reverse when moving forwards.
The only difference between N & D is the operation of the solenoids required for 1st gear and a clutch taking load. It's not a GM box with valve block made of cheese so I don't see a problem. Certainly less fuel is consumed idling in neutral than in Drive.
That LR write up is none too clear but from the ZF chart it can be seen that in P & N NO clutches are engaged.

brianp38dse · Feb 4, 2022

What is this Sport mode you all talk about

Henry_b · Feb 4, 2022

Datatek said:
View attachment 258279 View attachment 258279

The manual valve controls the fluid supply for P, R, N and D selector positions. The four solenoid valves operate accordingly to operate shift control, lock-up and shift quality. Solenoid valves MV 1 and MV 2 control the supplies that operate the brake clutches for shift
control. They are also used to prevent accidental engagement of reverse when moving forwards.
The only difference between N & D is the operation of the solenoids required for 1st gear and a clutch taking load. It's not a GM box with valve block made of cheese so I don't see a problem. Certainly less fuel is consumed idling in neutral than in Drive.
That LR write up is none too clear but from the ZF chart it can be seen that in P & N NO clutches are engaged.

Yes you're right..

However if you research HP22 failures

Datatek said:
View attachment 258279 View attachment 258279

The manual valve controls the fluid supply for P, R, N and D selector positions. The four solenoid valves operate accordingly to operate shift control, lock-up and shift quality. Solenoid valves MV 1 and MV 2 control the supplies that operate the brake clutches for shift
control. They are also used to prevent accidental engagement of reverse when moving forwards.
The only difference between N & D is the operation of the solenoids required for 1st gear and a clutch taking load. It's not a GM box with valve block made of cheese so I don't see a problem. Certainly less fuel is consumed idling in neutral than in Drive.
That LR write up is none too clear but from the ZF chart it can be seen that in P & N NO clutches are engaged.

The issue with the HP22 is free revving the engine in neutral, a slight deviation on my part. due to shaft seal wear the pressure won't depressurize fast enough and the A clutch drum partially engages in Neutral and it fries the clutches.

Only when it is revved in neutral

There was a service bulletin for it 24 01 91 (3196)

As for the D to N controversy everyone has there own opinion, I don't to it, but its up to the driver

300bhp/ton · Feb 4, 2022

HP24 in mine….

Datatek · Feb 5, 2022

Henry_b said:
Yes you're right..

However if you research HP22 failures

The issue with the HP22 is free revving the engine in neutral, a slight deviation on my part. due to shaft seal wear the pressure won't depressurize fast enough and the A clutch drum partially engages in Neutral and it fries the clutches.

Only when it is revved in neutral

There was a service bulletin for it 24 01 91 (3196)
No argument with that Henry, I always go to Neutral when stopped for more than a few seconds.

As for the D to N controversy everyone has there own opinion, I don't to it, but its up to the driver

kretslopp · Feb 6, 2022

Henry_b said:
Yes you're right..

However if you research HP22 failures

The issue with the HP22 is free revving the engine in neutral, a slight deviation on my part. due to shaft seal wear the pressure won't depressurize fast enough and the A clutch drum partially engages in Neutral and it fries the clutches.

Only when it is revved in neutral

There was a service bulletin for it 24 01 91 (3196)

As for the D to N controversy everyone has there own opinion, I don't to it, but its up to the driver

Is it the same in P?

Whenever I have drained some coolant and afterwards when bleeding the system I let the engine idle until it is as hot as possible and then to pressurize the system and let the water pump flow more I tighten the lid and then high idle for a little while. 2500RPM at most and then let it idle again and remove the lid to check if the flow from the top of the radiator is clear of air bubbles.
Repeat until that is the case.

Is this a really bad practice for the transmission?

Henry_b · Feb 6, 2022

kretslopp said:
Is it the same in P?

Whenever I have drained some coolant and afterwards when bleeding the system I let the engine idle until it is as hot as possible and then to pressurize the system and let the water pump flow more I tighten the lid and then high idle for a little while. 2500RPM at most and then let it idle again and remove the lid to check if the flow from the top of the radiator is clear of air bubbles.
Repeat until that is the case.

Is this a really bad practice for the transmission?

Depends on whether it is the hp22 or hp24, if you have the former then it isn't a good idea to rev the engine in P or N
2500rpm isn't too bad for it, depends on whether the A clutch drum has been engaged prior to revving it in neutral..

kretslopp · Feb 7, 2022

Diesel HP22.

So if the engine is started and gear selector is left in P. Then the A clutch has not been engaged at all? And therefore my air purging procedure is totally fine?

Henry_b said:
Depends on whether it is the hp22 or hp24, if you have the former then it isn't a good idea to rev the engine in P or N
2500rpm isn't too bad for it, depends on whether the A clutch drum has been engaged prior to revving it in neutral..

Datatek · Feb 7, 2022

kretslopp said:
Diesel HP22.

So if the engine is started and gear selector is left in P. Then the A clutch has not been engaged at all? And therefore my air purging procedure is totally fine?

Not a good idea IMO, nor is it necessary as the air can be purged with the engine idling.

Henry_b · Feb 7, 2022

kretslopp said:
Diesel HP22.

So if the engine is started and gear selector is left in P. Then the A clutch has not been engaged at all? And therefore my air purging procedure is totally fine?

Yes so long as D or any forward gears haven't been engaged then you'll be fine.

kretslopp · Feb 8, 2022

Henry_b said:
Yes so long as D or any forward gears haven't been engaged then you'll be fine.

Thanks, calm mode enabled again.

P38A Sport mode

Rubberknees

Well-Known Member

Datatek

Well-Known Member

brianp38dse

Well-Known Member

Henry_b

Think outside, no box required.

300bhp/ton

Well-Known Member

Datatek

Well-Known Member

kretslopp

Member

Henry_b

Think outside, no box required.

kretslopp

Member

Datatek

Well-Known Member

Henry_b

Think outside, no box required.

kretslopp

Member

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