300bhp/ton

diesels run at 18:1 CR or higher and they turn over no problem.

mattkimsey

I believe GM knows a good bit about OHC engines -- remember the ZR1 Corvette. It held the endurance record for over a decade using a stock motor and stock car. It was later beat by VW in '01 or '02 using a prototype car with a W12 engine -- far from production. Rumor is that GM had 470-480hp versions of these motors but the ZR1 was eventually cancelled. The car basically tanked in sales though -- the DOHC motor threw off the balance, added top heavy weight and was costly to make.

For most performance car buyers, I don't think they care how they get the power -- just that they get it! They also want it to be reliable and rather easy to "get along" with. This is where the OHV engine serves its purpose.

Look back at 1998 when the fbody came out -- 350hp in a $21k car! I don't think anyone else could match that in the US. The cheaper to build engine probably helped GM have more money to develope it and pass the savings on to the consumer.

Right now, and for the past 10 yrs, the LSx has simply been one of the best "packages" -- light, abundant, cheap, reliable, capable of massive streetable power, flat torque curve, easy to work on, low center of gravity, not bad on gas, small physical demensions, booming aftermarket, racing technnology from the C5R/C6R etc. -- you are simply hard pressed to find an easily avalible mass produced OHC engine with all these attributes.

The TVR Speed 12 V12 is a great piece of engineering, but it also cost $250,000, only 5 were made and the original intention of the Speed 12 was to contest the GT1 class of FIA GT motor sport and go to LeMans! If GM had 7.7L and that kind of money to throw into a specialty type motor -- I'm pretty sure we would see a 880hp pushrod engine with no more than 8.0L and lighter also. The fact is, GM has a budget to meet in order to sale something like its top of line pushrod motor in a 65k car “world class car” that they make 40,000 of.

I agree with you about the science of OHC supporting more specific output, but I also believe that the pushrod motor definitely has its place. We will likely see the evolution of the OHV motor in the next 2-4 years with GM now having 3v heads, 4v heads, dual cams, VVT and direct injection still to work with.

mattkimsey

Lets look beyond the superiority of OHC to make better specific output and we may find why Americans except OHV.

Lets say I want 505hp or 510hp and performance similar to a Z06 or Viper. I have $80,000 in my hand.

1.The S2000 is gone -- too slow.
2. Cars offering the 3.6 V6 are gone -- too slow.
3. TVR -- not offered here. Looking at Top Gears best runs -- the only TVR that comes close is the TVR Sagaris which is about $93,000 and it is still 2.2 seconds (a lifetime on such a short track) behind the Z06. Basically it's the fastest Top Gear tested TVR and it still doesn't come close despite costing $23k more.
4. Not even in the same class plus it's a small motor: http://www.evo.co.uk/carreviews/evoc...terham_23.html
5. What is the price here? $200k? If it's the F430 it still gets out performed

Second listing
1. Again cost? What do you get from Aston Martin for 60-80k?
2. Enzo?.....Enzo? $700,000 Enzo?

Ok, for 80k, I'll take the cars that surround a pushrod engine

300bhp/ton

Well Lotus Engineering does

Lotus did most of the earlier work on the LT5. There was also an American company involved that took the lead later in the production cycle. Lt5 was an awsome engine, but remember it's nearly 20 years old. And at that time the direct alternative OHV was heavy and massivly underpowered by comparison. Times have chanegd though.


True to an extent. But the reason it didn't go into production was Peter Wheeler, the then owner of TVR took one home one night and decided that it was too dangerous to be sold as a road car. BTW - the GT race cars actually had to be de-tuned to 660bhp. I think the Speed 12 is still the only GT race car where the road going engine was more powerful than the race one.

That I highly doubt, not a FULL legal productoin engine. Remember production engines have to meet much stricter regulations than we you for an annual inspection. Plus driveability and durability would be issues also. Again look at what the current LSx engines are like. 100bhp/litre is pretty much unheard of from a street going setup. And that means no cats, very noisey exhaust a cam which doesn't stand a chance of passing emissions and expensive ported big valve heads. Plus on these setups the motors are usually pretty usless in the low rpms. And have much increased wear on the valve train.

I love this **** thats always brought up when the Speed 12 is mentioned. Do you guys have any idea about TVR. They have hardly any money by coparison. And I would think GM probably spent similar amounts of money on the HUD for the C6 as TVR spent on the whole V12 programme. The are low volume car producer, maybe a few thousand units a year. BIG development budgets are not part of the business at all.

300bhp/ton

I know what you are saying, but I think this goes back to my comment on American's having a hard time accepting what OHC motors can do.

Now don't get me wrong, as I already posted I personally prefer OHV

And the reason being I like the throttle response, and low end grunt offered by them. So in terms of my personal preference I much prefer the driveabilty and power delivery of a typciall OHV motor.

But you are just using bad numbers. Yes a S2000 is not the answer, its just an example of possibility. Also you're pricing is well wrong. The Ł is strong against the $. So you claim the TVR Sagaris cost over $90k, were as in fact its the same preice as a Z06 over here (~Ł65,000). So for comparisons sake you need to also say a Z06 is $93k.

But again, just because there is an abscence of DOHC V8's doesn't mean they are bad. Take the S2000 again. Honda could quite easily turn it into a V8. And probably maintain the same specifict output. So you'd have a 4.0 V8 with 480bhp STOCK.

However Honda have no need to do this! V8's are pretty much an American market only engine. Japan they just would not sell or be suitable and the same goes for Europe. This is why you don't see these engines, there is really no real call for them.

GM and Ford could both do the same if they wanted. As they both have great DOHC s4 and V6 engines, but they are not used in the US very much.

Great example is the new Mustang. The V6 is 4.0 and has 210bhp, it's as old as the hills and is based off the aging Colone V6. But it suits the American market, as it has low down OHV grunt and is torquey to drive. Ford know this and thats why they used it.

Because they could have used the 3.0 DOHC V6 that we get, this has 230bhp and is lighter than the 4.0 V6 OHV. More power less weight? So why did Ford not use it? Because it has more of a European power delivery, more revvy. And not suitable for the US market.

There's also the fact that it would have meant the V6 would have performed too close to the GT. Better handling and stopping, and due to lighter weight it would probably have accelarated well aswell.

So I'm not disagreeing at all, because I genuinly like OHV engines. But my personal like doesn't alter their limitations.

300bhp/ton

Last quote

Ok, this is where the country you live in dictates the answers.

$80,000 is about Ł42,500 at present.

In the UK a Ford Focus coast about Ł12-14, C6 Vette Ł45k and a Viper Ł80k+

So choices would be limited.

Know if you want to talk direct alternative and we assume that 80k is Ł80,000 then yes you could buy a Z06 or a Viper.

But there are a lot of other cars in this price range:

-BMW M6
-Porsche 911
-Any TVR
-Marcos
-Mercedes
-Jaguar
-Noble
-Caterham
-Radical
-Ariel

and many more.

Now drag racing doesn't exist in the UK really. And racing on a circuit isn't everyday normality either. So many of these cars are certainly comparable, even to the Z06 in terms of outright pace on a public road. Several infact would be much faster.

But the price of the Vette and the Viper are shown up in terms of refinement and quality of components. They are plasticky inside. So you pays your money and you takes your choice.

Personally I love Ameican muscle (cough cough note the car in my sig). But a performance car is a whole package not just HP numbers.

dailydriver

300; I think he (Matt) knows/realises how small TVR is, and that is the point I feel he's trying to make here. They (TVR) do not have to justify/sell everything to a bunch of $h!theaded bean counters (especially nowadays) as the GM engineers MUST, in every case!! Being a small specialty marque run/owned by engineers/enthusiasts gives them that advantage.

slow

iTrader: (7)

Diesel motors also typically use 2 large batteries in parallel during cranking.

Ryan

Greg Fell

iTrader: (9)

Its all cylinder head. A big chief headed, big cube BBC can make 1000 hp no sweat NA as people said before.

z34_nut

iTrader: (7)

Are you really going to notice a difference between 700-1,00hp if you still can't hook?

300bhp/ton

True, well if I missunderstood - sorry.

Just in the past when mentioned it has been the typically comment that TVR spent more money on the V12 project than what GM does on an engine.

As I say if I'm wrong, my bad.

I doubt Matt will take it personally though, I know him from ages back over at Stangnet.

300bhp/ton

Mine doesn't.

slow

iTrader: (7)

is it a large displacement V8 diesel turbo? OR a smaller 4 cylinder diesel?

All the GM/Ford/Dodge diesel trucks I have ever worked on, have 2 large batteries.

Ryan

00transamnh

iTrader: (1)

such a ricer commnet... who says someone cant hook 1000hp?

and i beleive the original question was asked just because n/a hp is so much more badass than FI hp... (imo)

Greg Fell

iTrader: (9)

that makes at least 2 of us...8500 rpms of BBC makin 1000 hp = music to my hears. i dont get impressed w FI stuff, for the most part.

unit213

You certainly will around 70mph when that suckers finds some traction.

Louie83

iTrader: (3)

Not entirely true. Smaller cylinders are capable of higher RPM's. A 4 Liter V12 should out-perform a 4 Liter V6 due to shorter strokes, and smaller pistons, allowing greater RPM. The only downside is cost.

You would be right to say DOHC engines have an advantage of allowing 4 valves per cylinder. However, you are missing a BIG, HUGE, GIANT point.

HP = TQ x RPM / 5252

Do you not see that more RPM's equals more HP?

Have you not noticed that tiny crotch engines can make 200HP/L at like 15,000 RPM's?

Short strokes and tiny pistons equals high RPM's. Smaller engines SHOULD make more HP/L.

Why are OHV motors still around? They can make a lot of power per cost. If you want a lot of power and to keep costs down, sometimes OHV's are the right choice.

300bhp/ton

Agreed, well almost. At the end of the day there is only so a big a bang you can get in a cylinder.

But it's not just smaller its shorter stroke.

Yes, but that's the whole point, a OHV would not be able to sustain such rpms. It take DOHC tech to be able to do it, plus the thing called curtain area.

Ferrari 4.3 V8, has 5 valves per cylinder and manages 493bhp @ 8500rpm. Yet it's smooth and docile at 1500rpm. A 2v OHV motor will not be able to compeat at both ends of the spectrum.

Should have the potential maybe, not certainly will.

I hear this again and again, but no one has EVER been able to actually confirm OHV's are cheaper than OHC's to make.

Jaguar, BMW, Mercedes, Ferrari, Lambo, TVR, Lotus, Aston Martin and many others all make V engines (V8 and/or V12). However they are all OHC. And many of them are on a much smaller budget than those of the OHV setups.

TVR is again a prime example. Every single penny is important, yet they have made in house their own V8, S6 and V12. All where OHC. If OHV was cheaper why did they not use it?

Also why are most of the worlds V6's from Ford, GM (Vuaxhall), Honda, Mitsibushi, Nissan, Renalt, Peugeot, Rover, Mercedes, Porsche and many others all OHC and not OHV. Most of these engines are in low cost mass produced commuter-mobiles. So again the claim that OHV is cheaper seems contradictory to the actual motoring industry.

Specialized

iTrader: (15)

Another point that 300bhp/ton missed is a truity in any physics equation. Its not just the math you need to look at here. If you have a motor which makes 500lb/ft at 7200rpm, then thats great.. and it will make oodles of HP. But power is not all about HP, simply because you can state the equation and tell us that higher RPM= higher HP. You need the torque to be there too. If I find a motor which makes 1200 lb/ft at 4200rpm and a motor which makes 100lb/ft at 15000rpm, Thats a tripled rpm range and the HP calc will still not be even close. (5,040,000 vs. 1,500,000) The higher RPM statement doesnt really ring true, unless you can prove to me that it is physically impossible to make an OHV motor spin 10k rpms, and you can tune a OHC motor to have as flat of a torque curve as a OHV, then stop trying to prove mathematically that a motor of higher rpms automatically means more HP. Its in the PHYSICS, not the math. The physics behind the problem gives you the actual solution, and the math gives you the way to calculate it in terms of your understanding.

Louie83

iTrader: (3)

I was making the point that smaller engines are capable of higher RPM's and that is it. I'm NOT saying that OHC engines make insanely higher RPM's than OHV's of similar size.

300BHP/Ton gave the example of numerous SMALL DOHC engines making a lot of HP/L and comparing them to LARGE OHV engines that make less HP/L.

I was merely making the point that engines capable of higher RPMs, generally net higher Horsepower/L ratings. And the smaller the engine, the higher the RPM, the higher the HP/L. Go look for yourself at a bunch of 600cc crotch rocket power ratings. They can effectively make 200HP/L stock at a bajillion RPM's. It isn't because crotch rockets use far, far superior engineering to performance car engines.

Yes, torque is part of the equation, I'm not saying it isn't. Considering OHC does not have a major TQ/L advantage over OHV and OHV does not have a major TQ/L advantage over OHC, I didn't focus much on TQ. But if you cannot look at this equation (hp=tq x rpm / 5252) and tell me that an engine capable of more RPM's shouldn't have a potential advantage, then I don't know what to tell you.....well, maybe I do.

Let's say you have a 3L V8 and a very similarly engineered but larger 6L V8. Let's say they both make about 80lb/ft of tq / Liter for the sake of discussion. The 3L should to achieve a much greater RPM than the 6L (even if they had the same piston speed, the shorter stroke gives the 3L a blatant advantage). Therefore, the 3L should make a lot more HP/L than the 6L. That is the only point I am making.