@alivetuningltd could this be an injection timing issue? With the injector and piston relationship being brought closer together slightly but the cam to crank timing being the same, this would essentially have the same effect as the injector firing later in the cycle? Like tuning a petrol engine you would alter the ignition timing and read the spark plug? Are there adjustable cam gear options for the Td5? Just a thought....
Although power can be improved with some tweaking of the cam, it’ll still never be right, even with alterations to start of injection timing. It’s a truly bizarre phenomena and we’ve yet to find anyone who can actually explain the reasons, without talking $h1t!
Brilliant video.I imagine because you have lowered the injector in relation to the piston, the fuel atomisation may be compromised? Anyway very counterintuitive to skimming the head to raise the compression🤔
There’s no combustion chamber within the surface of the head, as theres a bowl with the piston. See our video from a couple of weeks ago and you’ll see. It’s a similar scenario when cutting injector seats too, where the injector nozzle is brought closer to the piston crown, although we’ve no evidence of this actually affecting performance.
I think the chamber in the piston (on direct injection) was developed by Dorman Riccardo. But its a long time since I was an apprentice, so I may be out of date now!
First I've heard of not skimming a TD5 head, why wouldn't it make the same? Every day is a school day! What should the bump gap measurements be, fully seated and back off a full turn? I do enjoy these deep dives with the dyno to prove changes. Finally, are the AMC heads less prone to warping? I know the injector seats are thicker.
This has been a thing we’ve been aware of since the Td5 was still young. Exactly why it loses power is a mystery, but it seems the more that’s taken off the head, the worse the outcome. The aluminium Td5 cylinder head is finished to exact dimensions, where as the otherwise rough cast steel block is finished to one of three levels, and an appropriate sized head gasket is used to make up the difference.
Regards the injector bump clearances, this needs to be: Rotate the engine so that the injector plunger is at max compression/highest lift on the cam. Crack off the locknut and wind the adjuster in until you feel it bottom out within the injector. Now turn the adjuster back one full turn, and lock it in place with the locknut. This is done on a cold engine. There is no gains to be made by running these clearances any tighter than one full turn back. Indeed where bump clearances are too tight, or too slack, the injectors can easily be damaged!
I have questions Was the same thickness of headgasket used? I:E: 2 hole for 2 hole? Was the head pressure tested? Were good quality parts used? Were the valves lapped?
There is a problem with this logic, you just increase the head gasket thickness if you skim the deck of the block, as the pistons will protrude further. If you read the manual it shows you how to measure for headgasket thickness. Skimmin the head does not bring the piston closer to the head. So you shoukd use the otiginal one. Skimmin the head does make the head more prone to wrapping as there is less material and the air swirling effect is lessened.
Another area that is often completely messed up is valve seats 90% of engine recon guys know nothing about valve seats and the specific geometry cut buy the factory ,the problem comes when the seats are recut and that geometry is destroyed loosing airflow and how the air enters the cylinder ,a good point is to take note of the seat angles throte id and valve hights especialy on inverted roller rocker valve train !!!!
@@diesel-technology5507 cylinder heads are flat on a td5 its not like a petrol that has dish in the head effectively the cc and compression ratio stays the same
@@diesel-technology5507 The C/R is unchanged! The Td5 cylinder head is completely flat faced, and so the only difference by skimming the head, would be the proximity of the injector nozzle to the top of the piston crown, and the amount of valve lift, although the lash adjusters should be able to compensate for a general head skim.
@alivetuningltd could this be an injection timing issue? With the injector and piston relationship being brought closer together slightly but the cam to crank timing being the same, this would essentially have the same effect as the injector firing later in the cycle? Like tuning a petrol engine you would alter the ignition timing and read the spark plug? Are there adjustable cam gear options for the Td5? Just a thought....
Although power can be improved with some tweaking of the cam, it’ll still never be right, even with alterations to start of injection timing. It’s a truly bizarre phenomena and we’ve yet to find anyone who can actually explain the reasons, without talking $h1t!
Brilliant video.I imagine because you have lowered the injector in relation to the piston, the fuel atomisation may be compromised? Anyway very counterintuitive to skimming the head to raise the compression🤔
There’s no combustion chamber within the surface of the head, as theres a bowl with the piston. See our video from a couple of weeks ago and you’ll see.
It’s a similar scenario when cutting injector seats too, where the injector nozzle is brought closer to the piston crown, although we’ve no evidence of this actually affecting performance.
I think the chamber in the piston (on direct injection) was developed by Dorman Riccardo. But its a long time since I was an apprentice, so I may be out of date now!
First I've heard of not skimming a TD5 head, why wouldn't it make the same?
Every day is a school day!
What should the bump gap measurements be, fully seated and back off a full turn?
I do enjoy these deep dives with the dyno to prove changes.
Finally, are the AMC heads less prone to warping? I know the injector seats are thicker.
This has been a thing we’ve been aware of since the Td5 was still young. Exactly why it loses power is a mystery, but it seems the more that’s taken off the head, the worse the outcome.
The aluminium Td5 cylinder head is finished to exact dimensions, where as the otherwise rough cast steel block is finished to one of three levels, and an appropriate sized head gasket is used to make up the difference.
Regards the injector bump clearances, this needs to be:
Rotate the engine so that the injector plunger is at max compression/highest lift on the cam.
Crack off the locknut and wind the adjuster in until you feel it bottom out within the injector.
Now turn the adjuster back one full turn, and lock it in place with the locknut.
This is done on a cold engine.
There is no gains to be made by running these clearances any tighter than one full turn back. Indeed where bump clearances are too tight, or too slack, the injectors can easily be damaged!
@@alivetuningltd Thanks for clarifying.
I see this has a snorkle as well. How mucu can this affect it or what needs to be done to make it okay?
I have questions
Was the same thickness of headgasket used? I:E: 2 hole for 2 hole?
Was the head pressure tested?
Were good quality parts used?
Were the valves lapped?
There is a problem with this logic, you just increase the head gasket thickness if you skim the deck of the block, as the pistons will protrude further. If you read the manual it shows you how to measure for headgasket thickness. Skimmin the head does not bring the piston closer to the head. So you shoukd use the otiginal one. Skimmin the head does make the head more prone to wrapping as there is less material and the air swirling effect is lessened.
It probably is down on power
Another area that is often completely messed up is valve seats 90% of engine recon guys know nothing about valve seats and the specific geometry cut buy the factory ,the problem comes when the seats are recut and that geometry is destroyed loosing airflow and how the air enters the cylinder ,a good point is to take note of the seat angles throte id and valve hights especialy on inverted roller rocker valve train !!!!
Skimming removes hardness because the head has been through a hot isostatic process
Makes more
Increasing the compression ratio always increases hp
The compression ratio remains the same, with the head skimmed or not. It’s completely unaffected.
@@alivetuningltd explain to me how lowering the cylinder head while maintaining the same stroke length doesn't raise the compression ratio slightly
@@diesel-technology5507 cylinder heads are flat on a td5 its not like a petrol that has dish in the head effectively the cc and compression ratio stays the same
@@diesel-technology5507 The C/R is unchanged! The Td5 cylinder head is completely flat faced, and so the only difference by skimming the head, would be the proximity of the injector nozzle to the top of the piston crown, and the amount of valve lift, although the lash adjusters should be able to compensate for a general head skim.
@@alivetuningltd piston to valve clearance is reduced, therefore the compression ratio has increased. There's nothing more that needs to be said
wheels and tyres lol