Glad i sat down and read all this topic It makes excellent reading material guys

Especially as i've raised the compression on my car

 

Fair enough MarkK, i agree with you there.

If i was building the engine im building currently for a customer, i would have a lower CR to encourage it to last, but as it is i will understand the level of mechanical sympathy i give it can have a very pronounced effect on its lifespan due to the PCP's and EGT's involved.

Its different building things for yourself to for other people.

 

You want top end BHP and limited torque anyway, so thats fine, you would break your gearbox weekly not monthly if you tuned yours like a "convential 350bhp YB" is done!

 

89XR2 it'ds completly on the side of this discussion and of course you are right, but un-resricted engine was considered only as an example or completly different aproach and to show why restricted engines are different form big power road engines.

 

I'd rather have less power and a high torque figure Fook the gearbox (which it probably would )

 

Thats why you do one a month already

 

Mark,
I've tried almost every possible configuration of compression, so I am talking from experience and am not blinkered at all. I totally understand what each change means as an on cost in other changes required. EVERYTHING brings with it compromises, but in my experience high compression brings the worse type of compromise (on pump fuel) and that is retarded ignition (for equal boost pressure on a lower compression engine).

Let's use Phil's engine as an example, a relatively low 7.9:1, but to stop it from detting at 32psi, he is forced to have MASSIVELY retarded ignition (Phil's engine is running single figures at high rpm ). This puts HUGE amounts of heat in an engine, and on a road car is totally unacceptable (I shouldn't think it is too sharp on a race engine either ). His engine shouldn't go bang, but his exhaust manifold and turbo might fall off wth the high EGTs / heat . Now he has quoted another tuner's car running even HIGHER compression, yet can't seem to grasp what that must mean to the ignition curve or boost curve - either or both of them must be severly retarded at the top end to give acceptable PCPs to stop the engine from going bang.

Ideally, you want something like Saab developed, which was a variable compression engine - now THAT was .

 

What comps have you tried, also how do you know what retard phil is running

 

7.2, 7.54, 7.8 and 8.0.

I know, because Phil told me .

 

Sorry Phil, but I read it as a diss...............I was about to post "TM dont be so rude - you dont know him well enough to call him that"

 

"retard phil"

 

Mike it starts in singles but as the revs rise so does the advance to double figures ...so not single all the way!

As i said you need to drive mine and compare it to your lo comp engine...you will find mine massively more a ROAD car engine than yours was!

Remember i had a lo comp version too.

 

Neither of which have EVER been live mapped . You hurry up and get your arse up to Norfolk, and you'll be eating your words about my engine compared to yours .

 

variable compression - dont know what came of it tbh,

as for the rest . ok

 

Saab are still working on variable compression engines.

Holy grail i reckon



What we need is solenoid operated valves for fully mappable "cams" and then mappable CR to go with it.

10:1 off boost 6:1 at 3 bar, 40mpg, and happily ever after


Oh and all installed on a 3 litred scaled down version of the LS1 with DOD!

 

i want a variable compression, camless engine

 

If the valves were operated with enough precision, you wouldnt need a throttle flap either of course!

Just fly a by wire variable resistor

 

Thats a bit harsh... never heard him referred to as "Retard Phil" before, plenty of other things, but never that!

 

Doh! Seems you all picked up on that one. That wil teach me to post before reading the whole thread!

 

might aswell ditch the spark plugs aswell

 

So what you are saying is as the revs rise, the cylinder filling gets worst and you can run more advance. Surely this shows why it is the dynamic CR of an engine that changes with cam timing, rpm etc is most important?

This is how the norwigiens (spelling) seem to get away with huge horsepower. high cr, wild camed engines???

 

No problem "retard doug"

 

Chip PLEASE get rid of the avatar which makes you look like a retarded hill billy

 

If it makes me look like that its a better likeness than i realised

 

I had a chap from lotus come to pick up a dash the other day said they ahve a cylinder up there with solenoid valves that they can test any cam profile on. He said the technology will hit the streets soon but in diesel truck engines to begin with as the valve gear/coils is still very big/heavy

 

Yeah but I'm double figures retarded, according to mike, phil is single figures retarded!!!

 

I think they just go for really high revs don't they?