Thoughts on supercharging v8v?

[baconsarney]

Been thinking of supercharging my four stroke mower no idea how to do it and it would still only mow the lawn as fast as I can push it. Bit of a non starter really...

[Emilio Largo]

Who would like to push a mower being the owner of a superfast Aston Martin? And what impression would that leave on all those women hankering after you?

If you chose a supercharged riding model, you could even take it to trackdays. Be a hero.

[Jon39]

MichaelV8V said:

You should probably think through the numbers on those videos, from memory, there is an assumption that if you supercharge a 2 litre engine and it gives you x bhp, then supercharging an engine more than twice the size will still just give you x bhp more. Even though at a given pressure, it will actually pack far more mixture into the larger cylinders of the bigger engine.

I looked at the figures.
2.0 litre = 47% power increase with 8 psi boost.
1.6 litre = 40% power increase with 12 psi boost.
4.7 / 5.0 litre = 21% power increase with 14.5 psi boost.

As you say, the biggest engine has the greater boost, but less percentage power increase than the other two.
Wonder what the reason is? Would you expect it all to be proportional?

I presume the main basis of the video, was to emphasise the importance of reduction in compression ratios.
I think GMR leave the compression ratio unchanged at 11:1, whereas the supercharged Jaguar in the video was quoted as 9.5:1.

[baconsarney]

Something not right there... I personally know TVR owners who’ve SC’d and turbo’d 5 litre Chims which have gone from just under 300bhp to over 500...

[RMDB9]

Does somebody have the performance stats 4.3 vs. supercharged?

[anonymous-user]

Jon39 said:

MichaelV8V said:

You should probably think through the numbers on those videos, from memory, there is an assumption that if you supercharge a 2 litre engine and it gives you x bhp, then supercharging an engine more than twice the size will still just give you x bhp more. Even though at a given pressure, it will actually pack far more mixture into the larger cylinders of the bigger engine.

I looked at the figures.
2.0 litre = 47% power increase with 8 psi boost.
1.6 litre = 40% power increase with 12 psi boost.
4.7 / 5.0 litre = 21% power increase with 14.5 psi boost.

As you say, the biggest engine has the greater boost, but less percentage power increase than the other two.
Wonder what the reason is? Would you expect it all to be proportional?

I presume the main basis of the video, was to emphasise the importance of reduction in compression ratios.
I think GMR leave the compression ratio unchanged at 11:1, whereas the supercharged Jaguar in the video was quoted as 9.5:1.

Compression ratios are part of it, but there's other variables that'll influence both the power increase and durability, and that's on any given engine. There's not really a formula to guarantee a set power increase, because each engine responds to power adders and forced induction differently, so increases aren't always linear. Some engines respond really well, others simply wont tolerate it. The Rover V8 is a good example; as much as the engine was adored by many for being the common man's price of admission into V8 power, the cylinder head design was terrible and it made little difference supercharging or turbocharging it as there were inherent flaws with the engine. It's why Wildcat head conversions were a better choice - as the engine's strangled and cannot breathe well enough without help, so forcing more air down its throat is somewhat wasted effort without making it burn fuel and air more efficiently. As I noted previously, swapping to a cam(s) with longer duration exhaust opening with greater lift, is often a necessity when you're putting more fuel air mixture into the chamber than the OEM cam spec expected.

I have experience with supercharging, albeit at the more extreme end, where the principles are broadly the same, but the numbers created are in an entirely different ballpark (boost levels between 30 - 50psi, and horsepower levels from 4000 - 10,000). All American V8's (those pushrod things that are seen as outdated but still seem to work decently for us racing reprobates ). The 6.5psi that the GMR setup produces, isn't huge, but if the blower's efficient (which a TVS is meant to be, as a hybrid / go between compared to a roots or screw blower) it's manageable so long as the engine's healthy. IMHO, I'd have the engine apart and upgrade a few areas before adding force induction though, but it's a personal preference.

I don't know of anybody other than Mr. GMR himself with a GMR'd car (have seen the GT8 demonstrator up close and it's a tidy installation, but that's not the issue being discussed). In regard to the dyno figures of that car (and I understand it wasn't necessarily 'standard' to begin with) IIRC they were carried out at JSRC. I've known John since the early 2000's when he raced in Street Eliminator. He's not a clown and isn't in the business of producing fairy tale dyno charts, so would have no reason to doubt the output. I've not seen a customer car equivalent that would validate it though.

[telum01]

Lots of interest in the kits but I'm not accepting orders for them until they're actually ready to ship. Too many production delays due to the pandemic.

I got ~550 bhp with a faulty fuel system.

As others have mentioned, there are plenty of n/a cars with aftermarket supercharger kits available. It's very common in the US given the lax laws we have that would otherwise restrict the modification in other countries.

My credit card they had on file expired. Spending a couple hundred dollars a month to sponsor a forum I almost never get on wasn't much of a priority so I didn't give them a new card to keep charging. Unpaid accounts automatically revert to "banned" to lock the account and force payment, but again I almost never get on forums anymore so I didn't bother.

I've been an extremely active member of this community for years. I offer tons of free information to help people own, maintain, and repair their Astons. I spend at least a few hours, if not several hours, every single day talking with owners and answering emails to help them out. I get told constantly that I'm either a partial or major reason why people have bought their Astons at all. I also travel (well, pandemic allowing) for Aston events and have met plenty of other owners, even hosted events myself and welcomed people into my home.

Edited by telum01 on Monday 12th April 19:23

[baconsarney]

telum01 said:

Uh, what? My credit card they had on file expired. Spending a couple hundred dollars a month to sponsor a forum I almost never get on wasn't much of a priority so I didn't give them a new card to keep charging. Unpaid accounts automatically revert to "banned" to force payment, but again I almost never get on forums anymore.

How does any of that make me less than reputable? And who do I owe money to? Do you know something I don't about my own finances?

I've been an extremely active member of this community for years. I offer tons of free information to help people own, maintain, and repair their Astons. I spend at least a few hours a day talking with owners and answering emails to help them out. I get told constantly that I'm either a partial or major reason why people have bought their Astons at all. I also travel (well, pandemic allowing) for Aston events and have met plenty of other owners, even hosted events myself and welcomed people into my home. I'm by no means perfect (nobody is) but you might want to get your information correct before you start accusing people of things.

[JonnyCJ]

baconsarney said:

telum01 said:

Uh, what? My credit card they had on file expired. Spending a couple hundred dollars a month to sponsor a forum I almost never get on wasn't much of a priority so I didn't give them a new card to keep charging. Unpaid accounts automatically revert to "banned" to force payment, but again I almost never get on forums anymore.

How does any of that make me less than reputable? And who do I owe money to? Do you know something I don't about my own finances?

I've been an extremely active member of this community for years. I offer tons of free information to help people own, maintain, and repair their Astons. I spend at least a few hours a day talking with owners and answering emails to help them out. I get told constantly that I'm either a partial or major reason why people have bought their Astons at all. I also travel (well, pandemic allowing) for Aston events and have met plenty of other owners, even hosted events myself and welcomed people into my home. I'm by no means perfect (nobody is) but you might want to get your information correct before you start accusing people of things.

Well said Rich !

[anonymous-user]

NFC 85 Vette said:

Compression ratios are part of it, but there's other variables that'll influence both the power increase and durability, and that's on any given engine. There's not really a formula to guarantee a set power increase, because each engine responds to power adders and forced induction differently, so increases aren't always linear. Some engines respond really well, others simply wont tolerate it. The Rover V8 is a good example; as much as the engine was adored by many for being the common man's price of admission into V8 power, the cylinder head design was terrible and it made little difference supercharging or turbocharging it as there were inherent flaws with the engine. It's why Wildcat head conversions were a better choice - as the engine's strangled and cannot breathe well enough without help, so forcing more air down its throat is somewhat wasted effort without making it burn fuel and air more efficiently. As I noted previously, swapping to a cam(s) with longer duration exhaust opening with greater lift, is often a necessity when you're putting more fuel air mixture into the chamber than the OEM cam spec expected.

I have experience with supercharging, albeit at the more extreme end, where the principles are broadly the same, but the numbers created are in an entirely different ballpark (boost levels between 30 - 50psi, and horsepower levels from 4000 - 10,000). All American V8's (those pushrod things that are seen as outdated but still seem to work decently for us racing reprobates ). The 6.5psi that the GMR setup produces, isn't huge, but if the blower's efficient (which a TVS is meant to be, as a hybrid / go between compared to a roots or screw blower)it's manageable so long as the engine's healthy. IMHO, I'd have the engine apart and upgrade a few areas before adding force induction though, but it's a personal preference.

I don't know of anybody other than Mr. GMR himself with a GMR'd car (have seen the GT8 demonstrator up close and it's a tidy installation, but that's not the issue being discussed). In regard to the dyno figures of that car (and I understand it wasn't necessarily 'standard' to begin with) IIRC they were carried out at JSRC. I've known John since the early 2000's when he raced in Street Eliminator. He's not a clown and isn't in the business of producing fairy tale dyno charts, so would have no reason to doubt the output. I've not seen a customer car equivalent that would validate it though.

TVS is still a roots-type supercharger, it’s just its rotors are more efficient than previous generations. Twin screw blowers compress air within the housing where roots simply move it from one side of the of the rotors to the other. Boost is made through resistance in the intake runners of the heads.

It’s true that power is a function of airflow and some engines will be able to make more than others due to a number of factors including limits of components, compression ratio, fuel quality and tune.

LS engines are super strong with 6 (cross) bolt main caps, well flowing heads and it’s quite easy to add 300-400hp to a 430hp NA engine with a change of cam and a bolt on supercharger. As a rule of thumb, assuming it’s not knock-limited, 1 bar boost will double HP of an NA engine, so about 800-850hp.

I would have thought a base 6psi would add about 100hp without stressing things too much? Whatever you do, make sure you get one with an intercooler!

Edited by anonymous-user on Monday 12th April 20:17

[Dewi 2]

NFC 85 Vette said:

I don't know of anybody other than Mr. GMR himself with a GMR'd car
(have seen the GT8 demonstrator up close and it's a tidy installation,
but that's not the issue being discussed).

Sometimes on here, there is talk about the UK Grigio Titanio Vantages (model year 2009 onwards).
One of those seven V8 Roadsters, does have a GMR supercharger fitted.
A 2010 car which is one owner from new.
Mileage at last MoT was 36,000, but I don't know when the supercharger was fitted.

There is another supercharged Vantage, seen competing at hillclimbs.
I don't know any more about that car, except that it does (might be sometimes) clock quicker times than a Vantage GT4 car, which was bought new and only used for hillclimbs.

Perhaps others here have more information.

[Jon39]

telum01 said:

Uh, what? My credit card they had on file expired. Unpaid accounts automatically revert to "banned" to lock the account and force payment, but again I almost never get on forums anymore so I didn't bother.

Possibly questionable behaviour when an internet platform openly publishes 'Banned', simply because they cannot obtain up to date card details. That word can so easily be misconstrued, as has been demonstrated.

A US President upset a different internet platform, but they then made it very clear on that site, why restrictions were imposed.

Glad you have commented here Rich. Sorry that the platform did that to you, and also that someone subsequently 'jumped to conclusions' on here.

[telum01]

Jon39 said:

Possibly questionable behaviour when an internet platform openly publishes 'Banned', simply because they cannot obtain up to date card details. That word can so easily be misconstrued, as has been demonstrated.

A US President upset a different internet platform, but they then made it very clear on that site, why restrictions were imposed.

Glad you have commented here Rich. Sorry that the platform did that to you, and also that someone subsequently 'jumped to conclusions' on here.

Yeah, that really put me off and was a major contributing factor for me not reinstating my account.

Anyway, hopefully the PH team take action and remove the person spreading libelous comments and this topic can get back on track.