SC Power conversions
Discussion
Yes you're correct, there will be a limit. You can't push 30 psi through a straw easily but you'd get it into a rover. The heads are naff when it comes to n/a big power but forced induction as you know will make epic torque etc.
With the right cam your engine would flow more power then that. All you're doing is shifting air, the cam doesn't know it's been compressed. So, a race cam or roller would work well if you want bhp.
With the right cam your engine would flow more power then that. All you're doing is shifting air, the cam doesn't know it's been compressed. So, a race cam or roller would work well if you want bhp.
SILICONEKID 345HP 12.03 said:
The LS is also very old fashioned and dated but it works .
The heads on the RV 8 are the limiting factor .
Not true at all, the LS engine has gone through a program of continuing development and capable of making big power with minor modification. The heads on the RV 8 are the limiting factor .
LSA and LS9 have piston oil squirters to keep the piston skirts cool and all have 6 bolt mains which make these engines capable of 1000hp with little more than new pistons and a pair of turbos.
LSX 376 B15 engine is designed for 1000hp and will make 2000hp if required with a stout iron block and 6 bolt heads.
The RV8/Buick engine is ancient and asthmatic by comparison.
Edited by anonymous-user on Monday 21st August 21:11
Edited by anonymous-user on Monday 21st August 21:12
wormus said:
SILICONEKID 345HP 12.03 said:
The LS is also very old fashioned and dated but it works .
The heads on the RV 8 are the limiting factor .
Not true at all, the LS engine has gone through a program of continuing development and capable of making big power with minor modification. The heads on the RV 8 are the limiting factor .
LSA and LS9 have piston oil squirters to keep the piston skirts cool and all have 6 bolt mains which make these engines capable of 1000hp with little more than new pistons and a pair of turbos.
The RV8/Buick engine is ancient by comparison.
Do they need to is really the question to ask. Pistons are designed to fit 'a design brief'. So, if lsa pistons do the job intended why would GM bother with the cost of going forged?
The LSA engine is like all the other ls engines. It'll be up to the task but will break if you push the envelope to far. The reserves aren't huge. I was telling that to the monaro guys years ago before they went on a s/c failure programme. They broke a lot of engines through bad tuning. Now they go forged if they want to make reliable extra hp. if you want more boost on an LSA you'll go forged.
The LSA engine is like all the other ls engines. It'll be up to the task but will break if you push the envelope to far. The reserves aren't huge. I was telling that to the monaro guys years ago before they went on a s/c failure programme. They broke a lot of engines through bad tuning. Now they go forged if they want to make reliable extra hp. if you want more boost on an LSA you'll go forged.
Edited by Boosted LS1 on Monday 21st August 23:09
Boosted LS1 said:
All you're doing is shifting air, the cam doesn't know it's been compressed. So, a race cam or roller would work well if you want bhp.
The cam doesn't know its being compressed, but the engine sure as hell does, ignoring the different valve timing requirements between a normally aspirated engine and one running forced induction is to miss a massive trick.In a normally aspirated engine valve overlap is used to good effect, the exhaust valve remains open when the intake opens, having both exhaust and inlet valves open at the same time initially seems counter intuitive but the strategy is deployed because at higher rpm the outgoing exhaust pulse creates a low-pressure zone behind the exhaust valve. This increases the pressure differential between the intake port and the combustion chamber helping draw in the new charge and so improving cylinder filling, in a way it's a form of free forced induction.
Overlap is very effective in normally aspirated engines but it only really works at higher rpm, the gasses need to be traveling at a high enough velocity for it to work, at idle and low rpm where gas velocity is low overlap is actually a bad thing and is part of the reason cars with a so called 'Race Cam' idle so poorly and are not nice to drive in town at lower rpms. This is where the brilliant idea of variable valve timing can give you the best of both worlds, ie little or no overlap at low engine speeds for a nice idle and good low speed drivability but then brings it in when gas speeds are sufficiently high enough for the effects of overlap to offer benefits.
In an engine using a compressor the air/fuel charge is being forced into the combustion chamber above atmospheric pressure so you don't really need the effects of valve overlap, indeed it can be undesirable as you run the very real risk of blowing some of the compressed air/fuel charge straight out of the open exhaust valve.
Interestingly the problem of blowing the air/fuel charge straight out of the open exhaust valve when both valves are open is worse on a supercharged engine because a supercharger is engine driven so has no effects on the exhaust side, a turbocharger on the other hand is exhaust driven so is a restriction in the flow of exhaust gasses. This restriction creates a back pressure which to some degree reduces the problem, but reducing the problem is all it does, it most certainly doesn't mean lots of overlap in a turbo engine is a good thing any more than in a supercharged engine.... it's just the problem is worse with a supercharger.
Quite clearly then if you actually sat down with a clean sheet of paper to design the best possible cam for an engine with forced induction it would end up looking very different to one designed for a normally aspirated engine. Taking it a step further the optimum cam design for a supercharged engine would look different to one designed for a turbocharged engine as you might choose to have a little more overlap on the turbo cam and almost none on the supercharged one.
Boosted LS1 said:
All you're doing is shifting air, the cam doesn't know it's been compressed. So, a race cam or roller would work well if you want bhp.
A race cam designed for a normally aspirated will have lots of longer duration overlap at higher rpm, so if you think about it a NA race cam would be far from ideal on a forced induction engine, especially a supercharged one as all it will do is bleed boost straight into the exhaust, raise exhaust temperatures, and ultimately waste fuel.SILICONEKID 345HP 12.03 said:
Why dont they fit forged pistons to thw LSA?
They don't really need to. The engine is rated at almost 600hp in standard tune. They are also designed for boost so have a thicker ring land than standard and are coated for improved lubrication. Change the cam, turn up the boost a bit and it will make around 800hp in otherwise standard form. Boosted LS1 said:
Do they need to is really the question to ask. Pistons are designed to fit 'a design brief'. So, if lsa pistons do the job intended why would GM bother with the cost of going forged?
The LSA engine is like all the other ls engines. It'll be up to the task but will break if you push the envelope to far. The reserves aren't huge. I was telling that to the monaro guys years ago before they went on a s/c failure programme. They broke a lot of engines through bad tuning. Now they go forged if they want to make reliable extra hp. if you want more boost on an LSA you'll go forged.
This ^ the LS is just a better blank canvas to start with rather the the aging RV8 The LSA engine is like all the other ls engines. It'll be up to the task but will break if you push the envelope to far. The reserves aren't huge. I was telling that to the monaro guys years ago before they went on a s/c failure programme. They broke a lot of engines through bad tuning. Now they go forged if they want to make reliable extra hp. if you want more boost on an LSA you'll go forged.
Edited by Boosted LS1 on Monday 21st August 23:09
progress and all that, but then to be honest I would even prefer to start with a 60's-80's cast iron small block be it Ford or Chevy anyway 
far more versatile and much wider and cheaper spectrum of after market go faster goodies 
I am still a RV8 fan-boy I am also a realist howeverChimpOnGas said:
A race cam designed for a normally aspirated will have lots of longer duration overlap at higher rpm, so if you think about it a NA race cam would be far from ideal on a forced induction engine, especially a supercharged one as all it will do is bleed boost straight into the exhaust, raise exhaust temperatures, and ultimately waste fuel.
This is true. The consensus amongst LS owners is for supercharged engines. Higher lift and durantion is preferable on the exhaust side with no overlap. However, you don't need a wild cam to make good power.^ As you probably guessed I'm referring to a turbo engine with exhaust back pressure. I've had fast road cams in turbo engines and they work just like a fast road cam but make more power then expected :-) Getting bogged down with camshaft charts and looking at valve overlap isn't anywhere near the same as living in the real world. just decide where you want your power and pick a cam that works in that region. You won't be disappointed if you keep things sensible and don't go to big.
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Boosted LS1 said:
^ As you probably guessed I'm referring to a turbo engine with exhaust back pressure. I've had fast road cams in turbo engines and they work just like a fast road cam but make more power then expected :-) Getting bogged down with camshaft charts and looking at valve overlap isn't anywhere near the same as living in the real world. just decide where you want your power and pick a cam that works in that region. You won't be disappointed if you keep things sensible and don't go to big.
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Good points, you can't beat hands on real world experience that's for sure.
But if I was running the Rotrex kit from SC-Power I'd definitely look to spec a roller cam with a specific supercharger grind.
Personally I'd be talking to there people...
http://www.thewedgeshopstore.com/roller-cam-setup-...
Interested comments by Boosted LS1.
I will find out what my turbo car is truly like tomorrow, when the car and I are at Snetterton.
To reduce overlap we have gone for a standard Range Rover cam.
It has massive torque (max around 50% more than before), but peaking in a narrower band than my old 5 litre engine with stealth cam. And BHP starts reducing from 5000 rpm. But peak bhp is presently set at 395, 80 more that I previously enjoyed.
My previous top speeds were 125 at the end of the start/finish straight and 132 at the end of the Bentley straight.
We will see.
I will find out what my turbo car is truly like tomorrow, when the car and I are at Snetterton.
To reduce overlap we have gone for a standard Range Rover cam.
It has massive torque (max around 50% more than before), but peaking in a narrower band than my old 5 litre engine with stealth cam. And BHP starts reducing from 5000 rpm. But peak bhp is presently set at 395, 80 more that I previously enjoyed.
My previous top speeds were 125 at the end of the start/finish straight and 132 at the end of the Bentley straight.
We will see.
ChimpOnGas said:
Boosted LS1 said:
^ As you probably guessed I'm referring to a turbo engine with exhaust back pressure. I've had fast road cams in turbo engines and they work just like a fast road cam but make more power then expected :-) Getting bogged down with camshaft charts and looking at valve overlap isn't anywhere near the same as living in the real world. just decide where you want your power and pick a cam that works in that region. You won't be disappointed if you keep things sensible and don't go to big.
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Some where in my the dark ages I drew up a chart of appx 50 rv8 and buick profiles that I found. I fitted a low overlap cam, it was useless unless I wanted to tow a caravan up a hill at 3000 rpm's. Later I picked a fast road cam, not to wild. It was really good as I had wonderful mid range torque and whoosh at the top end. I think it was a kent item, could even have been a 218. This was in the day's when it was fun crushing cosworths :-)
Good points, you can't beat hands on real world experience that's for sure.
But if I was running the Rotrex kit from SC-Power I'd definitely look to spec a roller cam with a specific supercharger grind.
Personally I'd be talking to there people...
http://www.thewedgeshopstore.com/roller-cam-setup-...
QB, I imagine you'll still be spinning in 3rd.
Two things I tried with some success may be useful. I squared the plenum off and fitted a pair of chargecoolers inside using a twin throttle arrangement. They worked well enough and I had a heat exchanger mounted across the boot in the lower section of a spoiler. This would be impractical on a tvr. It was also a fairly expensive conversion.
The other thing worked extremely well, is very diy and cheap. I fitted a home made water injection system that comprised of a water tank (large), a selonoid to open and shut the tank outlet via a switched ignition source. An adjustable pressure switch was set at appx 5 psi, some rubber hosing and a pair of welding tips that were fitted into the compressor inlets.
When the water flowed the engine became super quiet and smooth. It was a really good modification to do and I'd probably not bother with intercoolers again.
ETA, you need an electric water pump as well, doh.
The other thing worked extremely well, is very diy and cheap. I fitted a home made water injection system that comprised of a water tank (large), a selonoid to open and shut the tank outlet via a switched ignition source. An adjustable pressure switch was set at appx 5 psi, some rubber hosing and a pair of welding tips that were fitted into the compressor inlets.
When the water flowed the engine became super quiet and smooth. It was a really good modification to do and I'd probably not bother with intercoolers again.
ETA, you need an electric water pump as well, doh.
Edited by Boosted LS1 on Tuesday 22 August 14:06
PhilH42 said:
Where is he based Simon? MS2 seems a pretty good setup from what I've heard and read.....the right mapper close by was the only sticking point for me.
Shaun is based in Lincolnshire IIRC.Don't let that put you off at all, he will travel to you if needs be and his charges are extremely reasonable.
I've pm'd you a bit more detail
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