So i have a standard C20XE engine with a C30 Rotrex charger to add at some point next year
I intend to up the CR to around 11:1 with some forged pistons but the question i need answering is what some of cam profile am i ultimately looking
for?
My initial thoughts on CR has always been low as poss, loads of boost but the new way is to maintain a good CR and low boost as in the new OMEX/ROTREX
kit.
The zetec in JeffW's car runs 11.5:1 and is currently happy at 300hp(from memory).
Its basically the same when peeps are adding turbos too these days.
Bailey Performance(Dan-very helpful chap) does the same. They say that the car behaves very well, with good throttle respone(on std CR) and no
horrible lag due to an inefficient low comp engine.
I'm only quoting what others tell me here so dont shoot the messenger please
It just seems a great plan so i'm going to give it a try!
Not wanting to hijack but i have a Turbo engine that I'm part way converting to Supercharged and I yet to investigate whether it would be better
to use the Turbo cams or the NA cam for the engine.
quote:Originally posted by liam.mccaffrey
Not wanting to hijack but i have a Turbo engine that I'm part way converting to Supercharged and I yet to investigate whether it would be better
to use the Turbo cams or the NA cam for the engine.
For maximum drivabilty go for the standard cams. If you are after maximum BHP for track use then look at something more radical.
Best to speak to a specialist for your engine rather than trying to re-invent the wheel, trying to sort badly running turbo conversions can be soul
destroying..
quote:Originally posted by laptoprob
My initial thoughts on CR has always been low as poss, loads of boost but the new way is to maintain a good CR and low boost as in the new OMEX/ROTREX
kit.
The zetec in JeffW's car runs 11.5:1 and is currently happy at 300hp(from memory).
Its basically the same when peeps are adding turbos too these days.
Bailey Performance(Dan-very helpful chap) does the same. They say that the car behaves very well, with good throttle respone(on std CR) and no
horrible lag due to an inefficient low comp engine.
I'm only quoting what others tell me here so dont shoot the messenger please
It just seems a great plan so i'm going to give it a try!
The C30-94 in my car only makes 15psi at 100K rpm (the 94 is limited to 100K the smaller ones are 120K). Of which I get about 9psi at the plenum.
The engine is running forged pistons/rods (10.7:1 from memory so pretty much stock CR) and has ported/polished head with cams between Piper 285 and
mild race. Car produces 300HP at the wheels...
quote:Originally posted by snapper
Yep, do not increase compression to 11 to 1 with any sort of forced induction
You'll lunch the engine with detonation in seconds
That depends on the engine, the forced induction system and how well its tuned. High CR is more common on turbo / SC engines now, a turbo pinto would
struggle at 11 to 1 CR but a XE/zetec/duratec would be fines long as its tuned properly (not with guess work!)
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quote:Originally posted by snapper
Yep, do not increase compression to 11 to 1 with any sort of forced induction
You'll lunch the engine with detonation in seconds
That depends on the engine, the forced induction system and how well its tuned. High CR is more common on turbo / SC engines now, a turbo pinto would
struggle at 11 to 1 CR but a XE/zetec/duratec would be fines long as its tuned properly (not with guess work!)
HI Dan, knew you would be along anytime soon....
In your experiance on these setups am i btter off sticking with std cams and just trying verier pulleys?
My initial plan was to go for a flowed/ported head with some mediocre cams with a steadyish lift(286/11.5mm)?
The C30-94 in my car only makes 15psi at 100K rpm (the 94 is limited to 100K the smaller ones are 120K). Of which I get about 9psi at the plenum.
The engine is running forged pistons/rods (10.7:1 from memory so pretty much stock CR) and has ported/polished head with cams between Piper 285 and
mild race. Car produces 300HP at the wheels...
Spoke with Richard at TTS today who tells me that my C30-74 will happily put out 12 psi but the key is to make sure you keep as much as possible at
the plenum by using a good cooler with little pressure drop.
I would be a happy chappy with 300hp at the wheels but i'm searching for that at the fly so think its quite achievable looking at what you have
and also speaking with Dan@Bailey about his conversions.
quote:Originally posted by liam.mccaffrey
Not wanting to hijack but i have a Turbo engine that I'm part way converting to Supercharged and I yet to investigate whether it would be better
to use the Turbo cams or the NA cam for the engine.
Certainly with a decent cooler (air or water) mine would be well into the high 300s at the fly. Trouble is the gearbox/prop/English axle
wouldn't stand it. Until I can afford the Sequential box & high-spec Atlas there is little point.
quote:Originally posted by liam.mccaffrey
Not wanting to hijack but i have a Turbo engine that I'm part way converting to Supercharged and I yet to investigate whether it would be better
to use the Turbo cams or the NA cam for the engine.
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Building: Robin Hood series 3 + new project old Fury
posted on 13/12/12 at 06:45 AM
I once talked to a tuner in Colchester who was struggling with a high compression radical cam engine that the owner bolted a turbo to
Undrivable the tuner said, it comes on cam just as the turbo boost hits, driving it meant that it just span up its wheels as soon as you hit 4kand
went sideways
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
quote:Originally posted by snapper
I once talked to a tuner in Colchester who was struggling with a high compression radical cam engine that the owner bolted a turbo to
Undrivable the tuner said, it comes on cam just as the turbo boost hits, driving it meant that it just span up its wheels as soon as you hit 4kand
went sideways
quote:Originally posted by jeffw
My power curve is virtualy a straight line. The more you rev it the more power you get, there is no sudden kick like a turbo.
Have a look at this video down the straights to see what I mean
This is with my son in the car and I was taking it easy but you can get a feel for the linear power delivery. Remember to switch to 1080p
[Edited on 13/12/12 by jeffw]
Love the soundtrack and the way the engine responds. Never loses that revability that the turbos suffer with which is what sells it to me.
Do you or have you had any trouble with overheating and where did you put the intercooler?
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Building: Stuart Taylor ST1100 V4 BEC (built)
posted on 14/12/12 at 08:21 AM
Back to the original question, you actually want quite a tame cam. Sporty cams generally have loads of overlap to encourage scavenging of the exhaust
from the cylinders. In a forced induction setup you don't want oodles of overlap because you'll wee away all the PSI you've been
lovingly creating.
Regarding compression ratios it all depends on what boost level you're using, what fuels you're going to run, what level of intercooling
you're going to have, whether you'ld consider water or methanol injection etc etc.
You can run an engine on RON95 at 11:1 but you'ld be restricted on boost levels (prob high single figures) even if you run a goodly size
intercooler.
In my photo archive there's a scan of graph from G.Bell's Forced Induction Tuning showing recommended boost vs CR.
The intercooler is a Toyosport EBay special and the pipework was made up by Fury Sportscars when they did the install for me. It is very space
limited at the front of a Phoenix hence why the oil cooler is in front of everything.
The max plenum temp I see after a 20min track session is 50 deg C which is OK. It does drop 6psi across the cooler though.
quote:Originally posted by BenB
Back to the original question, you actually want quite a tame cam. Sporty cams generally have loads of overlap to encourage scavenging of the exhaust
from the cylinders. In a forced induction setup you don't want oodles of overlap because you'll wee away all the PSI you've been
lovingly creating.
Regarding compression ratios it all depends on what boost level you're using, what fuels you're going to run, what level of intercooling
you're going to have, whether you'ld consider water or methanol injection etc etc.
You can run an engine on RON95 at 11:1 but you'ld be restricted on boost levels (prob high single figures) even if you run a goodly size
intercooler.
In my photo archive there's a scan of graph from G.Bell's Forced Induction Tuning showing recommended boost vs CR.
These 'new-age' rotrex supercharged systems are effectively 'super' NA engines and the tuning is based on this idea. Low
boost (1 bar in my case) and high compression, big cams etc.
posted on 10/12/12 at 09:09 PM
