turbo pistons

[Reinhoud]

33 minutes ago, peter1127 said:

I don’t think the speed in which it spools up results in problems. Afaik detonation when turbocharged  occurs around peak torque, or at prolonged high rpm when everything gets ff hot. Both have nothing to do with spooling up. 
I can imagine a poorly chosen turbo heats up air more which doesn’t help.

efi and carbs both are fine as long as afr is correct.  You can run into fuel starvation with carbs when you turn down the pressure  too much to prevent flooding. Then again there are multiple ways to f up efi too :-)

I had a TD04 on my GS, kicked in nicely, had a bit of detonation. The VF20 I had  had quite a bit of detonation, spooled up real quick! The TD05 I had had hardly had any detonation, spooled up sort of slow, but still kicked in. Got a VF23 now, doesn't kick in, spools up even slower then the TD05, although it's smaller, no detonation at all.

 

So, according to my experience, the slower the turbo spools up, the less detonation.

Also, apparently, the slower the turbo spools up (or kicks in at higher RPM), the less change con rods fail... 

 

No expert, but I do have some experience with different set ups

Edited March 31 by Reinhoud

[Gixer1460]

1 hour ago, Reinhoud said:

In hindsight, I'm not sure that they don't have problems with detonation because of the EFI, or the sort of turbo..

I'd disagree! The fact that an EFI system generally can allow accurate fuel delivery - more or less - at any rpm or load and that ignition timing can be dialled in, also to those parameters means detonation can be minimised to the extent of being virtually un-detectable. It may still occur if a bad batch of fuel is used or climatic conditions are unfavourable but its unlikely to be engine destruction type det. As noted above, det. largely occurs around peak torque and as turbos can produce such wide torque bands the option to take out or add in timing in particular areas will reduce risk.

Personally, this is one reason I ask a dyno tuner to step tune when developing a MAP - go up rev range in steps and stop at each whilst allowing figures to stabilise and optimise fuel & timing there before moving to next step. It puts the engine under a LOT of load for minutes at a time and most tuners don't like doing it but I figure I don't ride at max rpm and max output at all times so I want these areas to be optimal not just at WOT!

[Reinhoud]

1 hour ago, Gixer1460 said:

I'd disagree! The fact that an EFI system generally can allow accurate fuel delivery - more or less - at any rpm or load and that ignition timing can be dialled in, also to those parameters means detonation can be minimised to the extent of being virtually un-detectable. It may still occur if a bad batch of fuel is used or climatic conditions are unfavourable but its unlikely to be engine destruction type det. As noted above, det. largely occurs around peak torque and as turbos can produce such wide torque bands the option to take out or add in timing in particular areas will reduce risk.

Personally, this is one reason I ask a dyno tuner to step tune when developing a MAP - go up rev range in steps and stop at each whilst allowing figures to stabilise and optimise fuel & timing there before moving to next step. It puts the engine under a LOT of load for minutes at a time and most tuners don't like doing it but I figure I don't ride at max rpm and max output at all times so I want these areas to be optimal not just at WOT!

Again,; I'm not an expert, I just wrote what my experience is.  But when you have a carburated engine you can also have a richer mixture..

How many EFI's run perfect? How many bikes have knock sensors?

I've seen quite a few dyno graphs with a crappy AFR line, while a carburated AFR line is almost perfect..

In theorie a EFI can be/should better then a caruretor, in reality, how many really are?

Edited March 31 by Reinhoud

[DAZ]

13 hours ago, Blower1 said:

Old boost calculation formula: (boost (bar) x compression ratio) + compression ratio = 16 or less is safe.
Above 16 needs intercooler and/or lower compression ratio.

 

7 hours ago, peter1127 said:

According to this 15psi at 9:1 is not safe (18) and maximum cr for 15psi is 8:1. Sounds conservative but indeed it’s safe. 

Surely boost is only one part of the equation ? Maybe I am wrong (and if I am I welcome being corrected as it is the only way to learn  )  but is boost not just a measurement of restrictions in the intake system ? E.g. If bigger throttle bodies or  intake valves  or porting allows more flow into the cylinder then the same amount of air would result in less boost pressure as measured in the plenum but the same cylinder pressure ?  Is it cylinder pressure that causes the Detonation an collapse of the ring lands (diesel-ing?) So maybe altering the valve timing to reduce cylinder pressure at lower rpm ?  Would 9.5:1 at 10psi but with better head flow be as powerful ? And still fit the formula ?

Edited March 31 by DAZ
Bleeding predictive text

[peter1127]

Yeah dynamic compression is a result of many factors of which you stated some. So what is true for one unique setup doesn’t need to be for  another, let alone different engines. That is why it’s so useful to get data from people with the same engine and a similar setup.