How much power can a stock RV8 4.6 take?
Discussion
Id say theyd handle it easily.
People assume that because an engine is developing more power/torque that its going to be a LOT more highly stressed, but thats not the case.
If you stay within the rev limits of the engine ther's no real reason to assume itll be any more unreliable than it already is.
Most stock engines made by anyone anywhere can handle 5psi of boost with no other mods to the engine so i cant see you having a great deal of trouble other than with heat/detonation control.
hth.
People assume that because an engine is developing more power/torque that its going to be a LOT more highly stressed, but thats not the case.
If you stay within the rev limits of the engine ther's no real reason to assume itll be any more unreliable than it already is.
Most stock engines made by anyone anywhere can handle 5psi of boost with no other mods to the engine so i cant see you having a great deal of trouble other than with heat/detonation control.
hth.
There's a good article about Rover V8s in this month's Practical Performance Car magazine.
Doesn't deal with superchargers, but does say that 4 litre and above versions (factory original size) have a stronger bottom end than smaller versions, and on a 4.6 can handle 340bhp no problem.
Doesn't deal with superchargers, but does say that 4 litre and above versions (factory original size) have a stronger bottom end than smaller versions, and on a 4.6 can handle 340bhp no problem.
Thanks for the replays.
I was thinking of a maximum of 7-8 psi, depending on the intake temperature.
The Dax Rush won’t have space for an intercooler. Unless I could fit one in WRX fashion.
The injection / ignition will be controlled by the MegaSquirt 2 when available.
See www.msefi.com/
The MegaSquirt should give me all the control I need and then some more.
I assume the 9.35 compression on the stock engine should be fine for the 7 –8 psi boost.
I have seen a very good web site from Phil, www.replica-cobra.co.uk
He uses a 3.5 Vitesse block with 9.75 compression and has 7.5 psi boost without any detonation problems.
Peter
I was thinking of a maximum of 7-8 psi, depending on the intake temperature.
The Dax Rush won’t have space for an intercooler. Unless I could fit one in WRX fashion.
The injection / ignition will be controlled by the MegaSquirt 2 when available.
See www.msefi.com/
The MegaSquirt should give me all the control I need and then some more.
I assume the 9.35 compression on the stock engine should be fine for the 7 –8 psi boost.
I have seen a very good web site from Phil, www.replica-cobra.co.uk
He uses a 3.5 Vitesse block with 9.75 compression and has 7.5 psi boost without any detonation problems.
Peter
Many of the expert tuners will tell you the 4.6 is a soft engine. Rev it beyond 5500rpm, and the crank or rods will break.
Until recently when my engine melted a piston ( no fault of the engines mechanical strength ) I had been using a totally stock 4.6 low compression short motor. I did have modified heads and cam etc.
The std pistons, although cast, are of a good strong design, in my opinion. Rods, Im not so sure about, but I never broke one.
My engine was a 4.6 twin turbo, pushing around 500bhp with 1 bar boost ( CR 7.5:1 ). This engine was in the car for around 18 months, and while not used everday, I did clock up a few miles, mostly to and from drag racing events, where the car was raced. Even on the road, the car was used as it was intended.
Apart from the melted piston, when I stripped the engine, everything was in excellent condition. The engine was revved regularly to 6k, although never for sustained periods. Just in gear.
I see no reason why 350bhp should present any problems at all, as long as mixtures are good, and there is no detonation.
Until recently when my engine melted a piston ( no fault of the engines mechanical strength ) I had been using a totally stock 4.6 low compression short motor. I did have modified heads and cam etc.
The std pistons, although cast, are of a good strong design, in my opinion. Rods, Im not so sure about, but I never broke one.
My engine was a 4.6 twin turbo, pushing around 500bhp with 1 bar boost ( CR 7.5:1 ). This engine was in the car for around 18 months, and while not used everday, I did clock up a few miles, mostly to and from drag racing events, where the car was raced. Even on the road, the car was used as it was intended.
Apart from the melted piston, when I stripped the engine, everything was in excellent condition. The engine was revved regularly to 6k, although never for sustained periods. Just in gear.
I see no reason why 350bhp should present any problems at all, as long as mixtures are good, and there is no detonation.
pitsnow said:
Thanks for the replays.
I was thinking of a maximum of 7-8 psi, depending on the intake temperature.
The Dax Rush won’t have space for an intercooler. Unless I could fit one in WRX fashion.
Have you thought about chargecooling instead (i.e. water to air intercooler with a secong water cooling radiator mounted remotely, say in what passes for the boot in a Dax Rush?
Fatboy
Yes, I thought about fitting a cooler in the boot space. However, the main problem is getting the required hoses passed the bell housing of the gearbox. There is no space what so ever there. I am currently thinking of moving the battery to the back. This is to get some space for the Efi parts.
Stevieturbo
I have looked into the possibility to fit the intercooler in the nose cone in Subaru WRX fashion, lying flat. This might be possible.
I have to see how much space is left after the 4.6 is in the car. My main problem will be to get the supercharger fitted. There is very little space in front of the engine.
And there is no space to the left or right of the engine. So the supercharger has to fit were the current distributor set-up is. I have the Serpentine front to the engine. This will allow me to use the timing information from the crank shaft.
The Rotrex C38 is about the size of an alternator. So it should fit in the space were the distributor used to be.
See: www.rotrex.eu.com/
Did you get the dosh for your Efi manifold? If not, my offer still stands.
Yes, I thought about fitting a cooler in the boot space. However, the main problem is getting the required hoses passed the bell housing of the gearbox. There is no space what so ever there. I am currently thinking of moving the battery to the back. This is to get some space for the Efi parts.
Stevieturbo
I have looked into the possibility to fit the intercooler in the nose cone in Subaru WRX fashion, lying flat. This might be possible.
I have to see how much space is left after the 4.6 is in the car. My main problem will be to get the supercharger fitted. There is very little space in front of the engine.
And there is no space to the left or right of the engine. So the supercharger has to fit were the current distributor set-up is. I have the Serpentine front to the engine. This will allow me to use the timing information from the crank shaft.
The Rotrex C38 is about the size of an alternator. So it should fit in the space were the distributor used to be.
See: www.rotrex.eu.com/
Did you get the dosh for your Efi manifold? If not, my offer still stands.
stevieturbo said:
Until recently when my engine melted a piston ( no fault of the engines mechanical strength )
Stevie, why did the #1 piston melt?
Was it running to lean? And if so, why was only #1 effected?
As you can imagine, it is a bitch to take the engine out of a Rush. It has to be installed and removed with the gearbox fitted!
Any info on how to prevent the engine from going bust will be appreciated.
And while I am at it, what about this clutch of yours which was for sale?
I do have a light car with a "heavy duty" clutch fitted.
But will the clutch cope with the increased power?
The supercharger does not produce the power as sudden as a turbo. But still, I may have to invest into a strong clutch as well.
Any thoughts on this?
Peter
I've blown my rovers as well. The 4.6 has a very good bottom end, the pistons are strong solid skirt items and all the internals are way better stuff then in the earlier engines. The rods are good to and have sps fasteners instead of nuts and bolts. You could use stock 9.35:1 C/R or look for an export lump. Stock engine will be limited to about 7-8 psi boost.
I had a chargecooler fitted across the boot beneath a spoiler but nowadays prefer water injection because it's so much more compact, cheap & adjustable. A chargecooler in the air dam would be best.
I had a chargecooler fitted across the boot beneath a spoiler but nowadays prefer water injection because it's so much more compact, cheap & adjustable. A chargecooler in the air dam would be best.
Boosted Ls1 said:
I had a chargecooler fitted across the boot beneath a spoiler but nowadays prefer water injection because it's so much more compact, cheap & adjustable.
I read about water injection on Phil’s web page. (see earlier post above)
Therefore, I assume you also control your water injection to come in above a certain air temperature and boost level? If so, how big a water reservoir do you use?
On the other hand, I don’t think that the average ambient temperature should be a problem in England with the boost level I am going to use. The whole system might run within safe limits even without any additional cooling of the intake air.
Peter
I did use an aquamist WI system on my car for a while, although found no benefit. My intercoolers are pretty good though.
It used very little water, and produced a very good mist, as the name suggests. A tad expensive, but a good product, if you are looking to reduce charge temps without intercooling. My temps were usually 30degC or less, although on some very hot days whilst waiting around to race they did reach around 50degC.
What about an intercooler mounted sideways along one of the flanks of the car, low down, with air ducted through it??? Surely there would be room for this ??
Although the aquamist system would be easier, as space it requires is minimal.
As to why no1... not too sure. Yes, I probably was running the car a bit lean, aiming for around 12.0:1 AFR, This was always ok, on the short blasts in my car, but on the Mountain section of the Isle of Man TT circuit, it was getting a lot of abuse, over a sustained period the car did feel better with the weaker mixture, but next time I think I'll stick with around 11.5:1 AFR. Much safer, and will still produce the goods.. Nice roads though.
Generally speaking , when such an engine melts a piston, one ( one piston, not number one ) always goes first. But there may be a design problem that causes a particular cylinder to go first.
Strange, that when another engine of mine let go a few years ago, a TT3.9 blowing through a holley, it dropped a valve seat ( due to detonation, my fault again ), with devastating consequences. It also did No1 cylinder.
From that, it cannot be inlet manifold deisgn, as both cars used totally different setups.
It could be my rather rough exhaust manifolds. Maybe a cooling issue with No1 cylinder ??
Dont know really.
It used very little water, and produced a very good mist, as the name suggests. A tad expensive, but a good product, if you are looking to reduce charge temps without intercooling. My temps were usually 30degC or less, although on some very hot days whilst waiting around to race they did reach around 50degC.
What about an intercooler mounted sideways along one of the flanks of the car, low down, with air ducted through it??? Surely there would be room for this ??
Although the aquamist system would be easier, as space it requires is minimal.
As to why no1... not too sure. Yes, I probably was running the car a bit lean, aiming for around 12.0:1 AFR, This was always ok, on the short blasts in my car, but on the Mountain section of the Isle of Man TT circuit, it was getting a lot of abuse, over a sustained period the car did feel better with the weaker mixture, but next time I think I'll stick with around 11.5:1 AFR. Much safer, and will still produce the goods.. Nice roads though.
Generally speaking , when such an engine melts a piston, one ( one piston, not number one ) always goes first. But there may be a design problem that causes a particular cylinder to go first.
Strange, that when another engine of mine let go a few years ago, a TT3.9 blowing through a holley, it dropped a valve seat ( due to detonation, my fault again ), with devastating consequences. It also did No1 cylinder.
From that, it cannot be inlet manifold deisgn, as both cars used totally different setups.
It could be my rather rough exhaust manifolds. Maybe a cooling issue with No1 cylinder ??
Dont know really.
I used a pressure switch to inject the water via an edlebrock $250 ecu/pcm gizmo. Worked a treat and used very little water and it was flow adjustable. As for good nozzles look for crop spraying tips/nozzles on the net. There are pcm's in oz for peanuts, look on the Autospeed.au web site.
cptsideways said:
Increasing the torque through the pistons will not directly damage the engine.
That isn't what I've heared from people who have done durability tests on boosted engines. 5-7 psi is OK as long as you stay away from detonation, but beyond that the gudgeon pins start to break out of the piston. Apparently the worst case for this problem is full throttle just under peak torque, this is where the pistons see the highest forces.
GreenV8S said:
Increasing the torque through the pistons will not directly damage the engine.
That isn't what I've heared from people who have done durability tests on boosted engines. 5-7 psi is OK as long as you stay away from detonation, but beyond that the gudgeon pins start to break out of the piston. Apparently the worst case for this problem is full throttle just under peak torque, this is where the pistons see the highest forces.
This also depends on the strength of the piston. Peak torque will be where the highest loads are but on a low pressure turbo engine those mechanical loads aren't much higher then on an atmo engine plus they're only there for milliseconds. Decent pistons can take this with ease and be durable. The detonation will kill any piston if you don't ease off.
With slotted pistons (early rover) then the crown can crack all the way across and detatch from the bosses. I haven't seen a pin breaking out though. Look at the stock early piston and you can see how weak it is. The new ones are much better and probably eutectic as well. 5-7 psi is a sensible limit for those early pistons.
Certainly looking at the std 4.6 pistons, they are very good. Crown is very thick, it has oil holes behind the poil control ring, instead of slots, and generally it looks like a very strong piston.
Generally speaking, HP doesnt break rods or pistons. Rpm's will, and so will detonation.
Ive turbocharged a few std engines ( not just rover v8's ) with std rods etc, and never had a problem, and most have ended up using around 20psi.
Generally speaking, HP doesnt break rods or pistons. Rpm's will, and so will detonation.
Ive turbocharged a few std engines ( not just rover v8's ) with std rods etc, and never had a problem, and most have ended up using around 20psi.
Hi all,
have been too busy to visit here lately so forgive my late reply.
I was told by rpi that any stock rv8 piston is only good for 300bhp, well, Ive proved them wrong. As has been said, as long as you stay away from detonation you will be fine, this is easily achieved with efi and water injection as a back up for high intake temperatures. Over reving is the problem, but thats easily held back with an msd or megasquirt. Dont wait for MSII, it will take a while before all the extra's that I and others have added to MS to come into MSII. Ive just released a version of MSnS that is specific for supercharged engines, its been running mine for a few months without problems. If I was you Id convert to MS asap then get the blower on then go over to MSII, its only a plug in modification.
I have no intercooler, impossible to make it fit, and to be honest, if Id have fitted one the loss of boost through it would have out weighed the gains through the lower intake temperatures. My temps are up to 50C on a very hot day when the car is moving, I do get a bit of heat saturation when stopped, intake up to 60C, but it soon drops when moving, and Ive changed the MS code to compensate for high intake temps by retarding the ignition timing to stop any detonation that might have occured during that period.
Phil
have been too busy to visit here lately so forgive my late reply.
I was told by rpi that any stock rv8 piston is only good for 300bhp, well, Ive proved them wrong. As has been said, as long as you stay away from detonation you will be fine, this is easily achieved with efi and water injection as a back up for high intake temperatures. Over reving is the problem, but thats easily held back with an msd or megasquirt. Dont wait for MSII, it will take a while before all the extra's that I and others have added to MS to come into MSII. Ive just released a version of MSnS that is specific for supercharged engines, its been running mine for a few months without problems. If I was you Id convert to MS asap then get the blower on then go over to MSII, its only a plug in modification.
I have no intercooler, impossible to make it fit, and to be honest, if Id have fitted one the loss of boost through it would have out weighed the gains through the lower intake temperatures. My temps are up to 50C on a very hot day when the car is moving, I do get a bit of heat saturation when stopped, intake up to 60C, but it soon drops when moving, and Ive changed the MS code to compensate for high intake temps by retarding the ignition timing to stop any detonation that might have occured during that period.
Phil
Hi Phil
My understanding is that the current MS cannot support the ignition without a distributor directly There are other boards required to run the ignition in a EDIS like set-up.
Due to severe space problems inside my engine bay, it is my intention to use the Serpentine front end, which has no distributor. The timing is taken of the crank in Ford EIDS fashion. This should give the space for the Rotrex C30 supercharger.
Since my project is going to take a wile (end of year earliest) to be completed, I was thinking of waiting until the upgraded version is available.
Cheers
Peter
My understanding is that the current MS cannot support the ignition without a distributor directly There are other boards required to run the ignition in a EDIS like set-up.
Due to severe space problems inside my engine bay, it is my intention to use the Serpentine front end, which has no distributor. The timing is taken of the crank in Ford EIDS fashion. This should give the space for the Rotrex C30 supercharger.
Since my project is going to take a wile (end of year earliest) to be completed, I was thinking of waiting until the upgraded version is available.
Cheers
Peter
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