Turbocharging a V8, advice
Discussion
Hi, you will need forged pistons, a compression ratio of 8.1 MAX even less if your going over 10 psi, ARP bolts in everything, and maybe splayed mains, proper blower/turbo cam, 2 electric fuel pumps(1 as back up) and a boost referenced fuel regulator set at 6.5psi for starters.You will also benefit from cooling the charge as much as poss, the meth injection kits drop the charge temp substantially.
Personally i would go with a procharger kit, more compact,cooler charge,more boost,and cheaper all round but you will still need all the engine mods listed above unless you run real low boost ofcourse.
Personally i would go with a procharger kit, more compact,cooler charge,more boost,and cheaper all round but you will still need all the engine mods listed above unless you run real low boost ofcourse.
Edited by BlownC4 on Tuesday 9th September 00:17
BlownC4 said:
Hi, you will need forged pistons, a compression ratio of 8.1 MAX even less if your going over 10 psi
It's interesting to see that you're recommending dropping the CR that far. How do you see the 'optimum' CR varying with boost e.g. 4, 8, 12, 16 psi? (Assuming adequate charge cooling.)
Its very much in the tuning and accurate ignition control. I have a Maestro 16V turbo which runs 24PSI at 8.5:1 and has no problems making a reliable 440BHP with water injection, without it I'm quite sure it would explode. My magnum runs 28PSI at 8:1 without WI but I run it rather rich at high boost. I don't think the bottom end needs much work. The AJP was designed to make much more than TVR ever extracted from it.
Jon
Jon
It is all in the tuning as said but there comes a limit as to how much boost you can run with high compression and the limit will be reached sooner then a lower compression engine. Given there's the opportunity to change pistons I would certainly go for a lower c/r as the greater bowl volume will allow a lot more fuel/air to be ingested, longer burn, more torque etc. Hopefully the car will be on boost most of the time so 8:1 or so should be fine. I usually plump for 7:1 and haven't had engines that are flat to drive off boost.
I apologise , the original question was requesting info from V engine builders.
If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
BlownC4 said:
Heres a good chart that should help explain.
That's interesting, but as far as I can see all it does is multiply the static CR by the blower CR. I would have expected the real behaviour to be somewhat more complex. For one thing, the compression associated with boost occurs upstream of the charge cooler so the system is no longer adiabatic. I also had the impression that the peak in-cylinder pressures don't (or needn't) go up in proportion to the nominal total CR. For example my 10.5:1 CR engine was fine with 0.3 bar boost just with the timing retarded slightly, not saying it's a recipe for reliability because I didn't do any reliability testing, but nothing nasty happened over several thousand miles. For 'phase 2' I've dropped the static CR a bit and will be adding an intercooler but still nowhere near as conservative as that chart suggests.BlownC4 said:
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
I think your being far to conservative, are you building 'old style' engines? Modern engines will usually handle 8 psi plus, reliably on stock internals in road applications. What engines are you building?So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
BlownC4 said:
I apologise , the original question was requesting info from V engine builders.
If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
Are you building carburettor engines with welded dizzy's for ignition ??If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
Get with time times. Even the "stuck in the dark ages" Cossie guys here are realising such low CR's are a thing of the past.
Yes, I might consider 8.0:1 as a CR for an engine.....well. Maybe not. Most recent ones Im working with, are higher than that, and we intend pushing over 30psi into them ( 4cyl motor )
When I rebuild mine, I'll be raising mine to a little over 9.x:1, and aiming for 20psi, perhaps more. Just have to see how it runs.
8.0:1 might be considered as suitable for something back in the 70's or 80's.....
Technology has moved on since then though.
Boosted LS1 said:
I think your being far to conservative, are you building 'old style' engines? Modern engines will usually handle 8 psi plus, reliably on stock internals in road applications. What engines are you building?
with all due respect did you miss this bit??BlownC4 said:
.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque,
Ive built many engines from mopars to chevys, i appreciate that modern engines stand more, but the question i asked has still not been answered........Exactly what kind of motor is being built here , a road motor with useable power or race motor?, as you know they are 2 very different things.stevieturbo said:
BlownC4 said:
I apologise , the original question was requesting info from V engine builders.
If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
Are you building carburettor engines with welded dizzy's for ignition ??If you want power and reliability from a V8 then my advice is relevant, if you want to build a race motor then you can push the boundries way more than my advice.
An 8.1 CR will not overstress the motor and allow the boost to generate the power easily, if you are upping the CR then you will need extra cooling such as meth inj or water inj, then you are in to a whole different world and BUDGET.I run EVERYDAY ON THE ROAD a 10psi boost on a 9.1CR and have no problems with 332bhp ATW and 400lbft torque, anymore than this would be undrivable, the motor will go upto 600hp and higher torque if i put alley heads back on and up the cam BUT you sacrifice reliability.
BMW deliberatly build ALL their motors to a much higher BHP then chip them down to give reliability ,they spend MILLIONS of pounds developing this system on every engine.
So you wanna build a V motor with high CR and big boost??? Fine but it will cost you £££££,s in blown motor parts.
Ive only built several hundred engines in my life so i dont profess to be an expert!
It all depends on the original post here, Do you want a WILD race engine???
Or
A daily driver with big power and reliability?
Get with time times. Even the "stuck in the dark ages" Cossie guys here are realising such low CR's are a thing of the past.
Yes, I might consider 8.0:1 as a CR for an engine.....well. Maybe not. Most recent ones Im working with, are higher than that, and we intend pushing over 30psi into them ( 4cyl motor )
When I rebuild mine, I'll be raising mine to a little over 9.x:1, and aiming for 20psi, perhaps more. Just have to see how it runs.
8.0:1 might be considered as suitable for something back in the 70's or 80's.....
Technology has moved on since then though.
Torque is what pushes you to the top.
Bhp is what keeps you there.
In theory.lol
This topic is about an AJP ,motor as far as im aware, an engine that was designed and built on a very tight budget by Al Merring, John Ravenscroft and ofcourse Peter wheeler, basically a heavily worked RV8, an engine that started as a 4.2 and was upped to a 4.5 but by all accounts the 4.2 was by far the better of the 2 and it was designed to churn out 350hp to compete with 911,s, something TVR struggled to achieve until they went to the speedsix.
I once met one of the famous 3 at the motor show and had a nice long chat with him about exactly this topic of releasing more hidden power from the motor, he laughed and said "that will be propaganda at work, do you think we would have settled for 350 if we could have reliably got more ?".
So...... he was obviously wrong and new nothing, he should have come here for advice. PMSL.
Edited by BlownC4 on Wednesday 10th September 02:44
BlownC4 said:
This topic is about an AJP ,motor as far as im aware, an engine that was designed and built on a very tight budget by Al Merring, John Ravenscroft and ofcourse Peter wheeler, basically a heavily worked RV8, an engine that started as a 4.2 and was upped to a 4.5 but by all accounts the 4.2 was by far the better of the 2 and it was designed to churn out 350hp to compete with 911,s, something TVR struggled to achieve until they went to the speedsix.
Sorry I had to quote that just so I can come back for a laugh every now and then ..Blown C4 looking at your setup its generally thought of that lower comp is better! the old root systle blowers make alot of heat when worked hard. ok thanks to the pull through carbs the temps are much lower but its not the best way to cool the intake. modern motors will take much more boost as standard. as said LS1 have run ALOT of boost straight outn the box.
its worth taking a look at the nelson racing engiens site. there are some articals on there abount an engine they built for a mag (think it was hot rod). gose into quiet a bit of detail about what they do. one coment was that ignition really is key! once you ahve that sorted its easy to make power reilably.
As for the ALP, i guess no one really knows! lol
Chris.
its worth taking a look at the nelson racing engiens site. there are some articals on there abount an engine they built for a mag (think it was hot rod). gose into quiet a bit of detail about what they do. one coment was that ignition really is key! once you ahve that sorted its easy to make power reilably.
As for the ALP, i guess no one really knows! lol
Chris.
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