DavidNJ

Remember that 1990 electronics is not 2006 electronics. A modern development of the LT5 would probably easily be in the 500-550hp range, emissions legal. With a very broad torque curve.

rons 00z

iTrader: (10)

i wouldnt imagine it would take much to blueprint that motor to make some decent numbers. say a bigger cams port work bump compression and you'd have a winner

RussStang

I don't know about that. Scroll down to the second article on this page.

http://www.autozine.org/0_News/Archi...5_07/News.html

AMG uses some kind of coating for their cylinder linings, instead of sleeves, and I would imagine boring the engine out from its stock form would get very costly very quickly. They also remark that the v8's bore distance is 109mm (4.29 inches). I am unsure as to whether they mean the bore itself is 4.29 inches, or more likely it seems to me that they mean its bore center to center distance is 4.29 inches. I am not sure of the engine's bore and stroke dimensions, but I would imagine that with a roughly 4.3 inch bore spacing that a 6.3L v8 built to rev (and probably oversquare in the process) is going to have problems sustaining much of an overbore.

speedz06

All this has made me want to say something I've been thinking about when I think about engines;I'm willing to bet that in our lifetime we'll see the pushrod engine practically disappear from all auto makers product lines.I personally look foreward to the possibility of getting the high revs that many motorcycles are now realising(upwards of 14,000 rpm).I'm still wondering why the OHC multi valve car engines are turning much less than they could.I saw some kind of OHC conversion for GM V*'s once.My LS engine runs pretty damn good though.

300bhp/ton

Yeah it's called Nikasil coating and has been proven with motorcylce engines. Jaguar also used as did the Porshce 928 I think. But they had some issues with it due to poor fuel quality a few years back.

http://en.wikipedia.org/wiki/Nikasil

RussStang

I bet guys in the 60s and 70s felt the same way. Pushrod engines have survived as long as they have, and I doubt they are going to go away anytime soon. Hell, Chrysler just adopted a pushrod engine as its mainstream v8 (Hemi). Anyone who has driven an LS1 car knows how smooth the engine is, despite being a pushrod engine. They are cheaper to build, and still give strong hp numbers. Prostocks run 500 cube v8s and rev them to 10k, and naturally aspirated the things make 1300-1400 hp. That is well over 100hp/liter, although they are race engines.

Revs don't come only from the top end. I really doubt the bottom end of a street engine is going to enjoy seeing 14,000 rpms ever. Motorcycle engines are very short stroke engines, and most motorcycle engines don't see the kind of mileage and automobile engine does. I know guys who start noticing oil consumption in there bikes with 10,000 miles on the odometer.

I don't see anything with over a 3" stroke revving to 14k in a street engine, regardless of valvetrain. BMWs new 5L v10 revs to 8k, but it also has the benefit of having two extra cylinders to help create displacement, and it is a lower overall displacement engine as well (less rotating mass). The LS7 revs to 7k straight out the door with a 4" stroke. Destroke an LS7 and add two cylinders two it and I could see an LS7 being able to pull 8k rpms.

I am well aware of the inherent benefits of an OHC valvetrain, and for extremely high rpm levels they are superior. It is unlikely that anywhere in the near future Formula 1 will adopt a pushrod setup at the rpms they are pulling. I just don't see why some of you think a pushrod engine can't cut it on the street. Porsche/BMW/Ferrari engines don't have a high specific output given their displacement simply because they are OHC engines. They have a high specific output because they are very high tech, expensive *** motors. If GM built a really high tech, expensive pushrod engine I am sure it would have a much higher specific output over the stock LS motors as well, but it kind of defeats the benefit of the cheaper cost to build a pushrod engine.
Here is a pretty cool pushrod v8 that GM built, but it is likely only to stay a concept.
http://autospeed.drive.com.au/cms/A_1193/article.html
This would allow for full variable valve timing on both the intake and the exhaust seperately, as opposed to the VVT that will be equipped via Cam Phaser to the LS blocks now, thanks to its two independent camshafts.

300bhp/ton

For most of the world they will. Except perhaphs in diesels as they tend to work very well there even in 4 cylinder guise. I mean how many main stream push rod production engines are built for the world market. The Lsx engines where only evey sold in very low volume as specialist cars in Europe, the same goes for the new Hemi. They are not common. In percentage terms OHC/DOHC has an overwhelming advantage.

In all honesty I LOVE the LS1 (I do have one ), but having driven engines like the V12 Jagaur engine it makes the LS1 feel as rough as sand paper. Even the old Jaguar straight 6 is a far smoother and refined engine, so are the BMW straught 6's.

The LS1 is good, but it's power delivery is quite raw and unrefined by comparison. If you don't beleive me, you need to go and drive a Jaguar V12, pref an early 5.3 EFI, they are one of the smoothest engines I have ever witnessed. And this includes having first hand experiance with a twin turbo 6.75 Bentley V8, a W12 Bentley, a 3.5 Ferrari V8 and a 5.0 Marcedes V8. In refinment terms the Jaguar V12 is in another league.

I have no idea of production costs per unit, but I can't believe they are really cheaper. If they where no one would build OHC 4 cylinder engines, yet I can't even think of an OHV 4 cylinder engine that's been in production in the last 20 years. But yes they DO give strong HP.

Hardly relavent to a road engine. Not to mention the durability of such and engine and it's fuel requirements.

I'm a firm believer that on a l"ike for like" basis a DOHC engine of the SAME capcity will always out perform a 2v OHV push rod engine.

Regardless, high rpm OHV engines are pretty rare. The LS7 is an exception but it's hardly a 'run of the mill' example considering it's a purpose built high eng performance engine which is hand built. It also runs a dry sump lubrication system, which I guess is really needed to maintain durability of this kind of engine so it's fit for production and so GM can warranty it.

I like

I personally love OHV engines and in many ways I think they are superior road engines as they tend to produce very good torque and low end grunt with a responsive throttle response. So no despite the technical ability of OHC I do really like and prefer OHV for a road engine. But in competition I do still believe OHC is superior, it's only the fact that most OHV engines have a large displacement advantage that they can be competative.

No I don't agree there. They are not really any more hi-tech than an LS1, they acheive their efficency by being OHC engines, it really is that simple.

OHC can run a higher state of tune and still remain reliable, durable, emission & noise legal. Push rod engines just don't manage this. I mean how much effort is it to get a 5.7 LS1 to produce 570bhp (flywheel)? Then do you think it could be done and still remain FULLY legal in every respect (noise & emmsions) and be tractable and driveable, along with good enough reliability to last the life time of the car (or even 100,000 miles) with out a rebuild, and also be economical?

There are many many DOHC engines that run the same state of tune or even exceed it. Yes they produce overall less bhp, but that's due to their displacement not the principle of how they operate.

What do you mean by hi-tech??? What do the OHC engines have that the push rod does not?

I mean the Lsx engines are all aluminium, running with an advanced EFI system controlled by ECU's & PCM's. The LS7 uses many exotic components and dry sump lubrication. It uses an active exhaust system. And is hand built. There's also a new cylinder control system which can actually shut of cylinders under light throttle to make it more economical. VVT is possible also.
So what do all these OHC engines have?????

300bhp/ton

Looks pretty funky, although with a 4.3 litre capcity it still only produces 295bhp (68.6bhp/litre) and 295 lb ft so it's not exaclty ground braking statistics. But who knows maybe it's in a really mild state of tune.

I would think such an engine has a strong possibilty of production, provided it doesn't cost too much to produce.

RussStang

That is not a fair comparison. Straight 6s are known for being inherently balanced in their design, and v12s are even moreso, given their natural balance and more power pulses per crank rotation. I am not trying to say the LS1 is the smoothest engine out there, because that certainly is not the case, but given your average run of the mill engine in a commuter car, the LS1 feels fine compared to its competition.

4 cylinders are always OHC because
1. There are only 4 cylinders. OHC engines are more expensive to produce, but given that a DOHC 4 banger only has one bank of cylinders, I would suspect they still cost a good deal less than any v8, pushrod or not.
2. They are typically much lower displacement, and need every performance aid they can muster to create acceptable hp levels, especialy in todays extremely competitive marketplace.

LS2s run a 6500rpm redline. Doesn't seem that much lower to me. LS1s are known to be able to handle over 7000 rpm without much drama, as long as the oiling system and crappy factory rod bolts are accounted for. As you stated, high rpm OHV engines are pretty rare, but overall in the world market OHV engines are pretty rare as well.

One of the benefits of an OHC engine is typically better throttle response, so I am suprised to hear you say that. DOHCs can produce low end grunt too, it is more a product of cam selection and motor displacement than straight up use of pushrods.

Well, I don't agree with you at all here. Are you honestly trying to tell me that a F430 motor is not anymore high tech than an LS7? How about the new M5 motor, with 3 32bit processors on board monitoring the engine and making corrects and such, and individual throttles for each one of its cylinders, straight from the factory? It really isn't as simple as you are trying to make it out to be. Remember, these engines are running 4 camshafts. The placement of these camshafts certainly makes an impact in the design of the engine, but the LS engines are only running one. With the state of today's technology and metallurgy, I don't really see the pushrod being much of a handicap at all in a street motor (race motors are a different story). The handicap I see in today's pushrod motors are due to the fact that they only have one camshaft controlling both the intake and exhaust events, and that they are all 2v engines. A 4v setup would be really nice to see, but again, would probably negate much of the benefit of a pushrod engine's inherent lower cost.

Your first sentence in my eyes is rubbish. There is no advantage to an OHC as far as realibility, durability, emission, and noise legality go. I don't know how many pushrod engines you come across in England, but I have seen many more than a handful with 200,000 miles on them and still running. How does an engine being pushrod affect its noise levels? What does having pushrods do with its reliability? You don't think a pushrod engine will go over 100,000 miles without a rebuild? Nonsense.

Typically 4 valves per cylinder.

What is so advanced about the LS7's PCM? It certainly is no BMW PCM, and I have read Ferrari has put quite an effort into their electronics as well. Hand built does not make an engine more technological. I don't see how exotic components do as well. There is no cylinder shutoff on the LS7 (which does nothing for power production), no VVT, the exhaust system is not really they high tech (it is just a valve that opens above 3500 rpm under heavy loads, I don't see what is so high tech about that).

Besides all of that, the LS7 is built in an extremely mild state of tune. You do know that with a cam swap and a set of headers the things are making between 550-600rwhp? Gonna be pretty hard to get that out of an M5 engine or a Ferrari v8, and its never gonna happen n/a.

There is really no room for arguement here, because you are right.

Again, I agree.

A seperate camshaft to control intake and exhaust events, and typically more valves per cylinder. None of this is the pushrod's fault, but at the moment all pushrod engines are built with one cam in the block, and 2v per cylinder, so there is really no way around this. I have seen 4v head pushrod engines, but never a 2 cam in block engine like the GM XV8 concept.


Look, I am not a pushrod engine lover. I just feel that they make very acceptable engines at the street level today, and with the metallurgy we have in this day and age, give up little to the OHC engine. There are no "performance only" pushrod engine built today, even the LS7 has it's humble underpinnings in a GM design that requires being modular to both car and truck platforms. GMs pushrod engines are far from being maxed out from the factory, and I doubt we will see one anytime soon that is, all due to manufacturer cost. I just don't think it is as black and white as you are trying to make it out to be. OHC design has direct performance advantages over OHV design, but I hardly think that is the only viable criteria for comparison between the two engine types today.

DavidNJ

You are missing it. DOHC is winning because of variable cam timing used to meet emissions laws. Is it cheaper to make? Yes, if you count meeting emissions laws. It only became that way with modern computer controls. As late as the mid-90s, MB went with a SOHC twin-plug design, no dropped.

A straight six or V-12 will be smoother than a V-6 or V-8. Balance your LS1 and use a mild camshaft (say 220 seat time) and you can balance a coin on it. The trouble is the guys using balanced rotating assemblies are also using 240@.050 cams.

The LS1/Hemi fit an interesting niche of low cost high power engines. Used more in trucks than cars (35k Corvettes plus some Monaros vs how many Suburbans, Yukons, Escalades, Sierras, Hummers, etc.), these engines will be with us for at least another 5-10 years. Marketing alone will keep the Hemi alive.

MB apparently will have a turbo version of the 6.3. However their numbers are always limited by the driveline and the milktoast cars they go into, not the engine's potential.

Look next for zeroshift transmissions and Rotrex superchargers. Personally, I would prefer a 3L 400hp 2400# car with a Rotrex and zeroshift. It would probably match a C6Z06 to 130, better traction off the line, better handling, better braking, more agile.

300bhp/ton

I was meaning with specific referance to state of tune.

A DOHC engine can produce 100bhp//litre as a production engine meeting all criteria. I know of no OHV push rod engine that can claim this.

A Honda S2000 engine rpoduces 120bhp/litre and will last as long as any OHV V8 will.

If only that knid of specific output was acheivable with OHV, then we really would see some impressive bhp numbers from STOCK engines.

Louie83

iTrader: (3)

The little motorcycle engines get high rpms because they are smaller more then the fact that they are DOHC.

Think about it, for a big pushrod engine to complete a cycle, it's pistons must move a much greater distance to complete a cycle than a tiny DOHC engine with tiny pistons. If both engines pistons are moving at the same speed, the little DOHC engine still has a higher RPM because the pistons do not have to move as far to complete a cycle.

Horsepower = (Torque * RPM) / 5252

So naturally a smaller displacement engine will have more HP/Liter than a larger engine since higher RPM's are easier to achieve. This is the main reason why ricers who brag about HP/Liter are so retarded.

MadBill

I would think the main criteria for a powertrain should be performance, fuel economy, cost, smoothness... If you left the hood shut and taped over the tach, would you really know what your BHP per liter was, driving say a Cadillac CTSV vs. a similar cost/size Mercedes?
BTW, around 1990 when I was working on a couple of GM racing programs, the manufacturing cost of a 2.2 L 170 HP Oldsmobile Quad four was more than double that of a 240 HP 5.7 L. Tuned Port Injection Chev.
Also, my wife's 240 HP 3.8 L. pushrod V-6 Buick Park Avenue gets 40 MPG (Imperial) at 60 MPH, about the same as my 1.8 L. I-4 16 valve 5 speed Vibe...

Louie83

iTrader: (3)

Is that more due to the fact that it is DOHC, or that it is a small engine. Read my last post.

RussStang

Thank you.

Apparently you are missing my point. The F20C in the s2000 is built ***** to the wall as a performance motor, without much to compromise. It is a very expensive 4 cylinder engine. It might even be more expensive than a freakin LS1 V8. LS1s are built to be cheap. They may not make alot of specific output for their size stock, but they still do make considerable power straight from the factory, and are very cheap for GM to produce. These motors have alot of aftermarket potential, but straight from GM they are not the ***** out performance engines that the F20Cs are, regardless of what marketing might say otherwise. If the LS1 was built only as a performance motor, straight from the ground up, and didn't have to also find its way into GM's trucks, and was built up to a degree that the F20C is, than the LS1's specific output would be much closer to that of the S2000s. It wouldn't be as high as the Honda's but it would have bridged that gap considerably more than what it does now. However, GM has to do things on a budget, and the LS motors are modular engines, that have to find there way into multiple types of vehicles. I am sure the guys that worked on the Corvette's powertrain would have prefered something with less than 4" of stroke for the LS7 and more bore, but they can only work with what they are given.

My point is that the LS series engines were born out of compromises, and making comparisons between an LS engine and a freakin uncompromising flatplane Ferrari engine is ridiculous. It is not exactly comparing apples to apples. If someone out there built a pushrod motor straight from the ground up as only a performance engine, and had little to no budget constraints in the procedure, then that would make for a good comparison. However to me this seems unlikely, because someone who might build a motor straight from the ground up for performance is likely to go OHC anyway to give the motor as many strengths as possible.

RussStang

Actually I have heard complaints from many owners who have driven their s2000s hard for much of the car's lives that the motors develop of habit of consuming abnormal quantities of oil (not that there are LS1s out there that don't do this either).

300bhp/ton

So how do you explain the 7.7 litre TVR V12 with 880bhp?

Louie83

iTrader: (3)

It's a damn impressive and damn expensive engine. That does not mean what I stated is not true.

A Yamaha R6 ( .6L DOHC ) technically makes 205bhp/Liter. Your TVR makes about 114bhp/Liter.

Does that mean that Yamaha engineers know something that TVR engineers don't? No, that TVR engine is far more impressive than the Yamaha R6 engine do to the reasoning I explained above.

Also, all this talk about peak HP is making me feel like I am on a Honda board. A car accelerates fastest at its peak TORQUE for any given gear, not it's peak HP. DOHC's cc for cc can usually create more peak HP than a OHV (because they can rev higher), but for torque that is not the case. Also, the area of the hp under the curve and the area of the torque under the curve are obvious a better testament to the power of the engine than looking at peak numbers.

RussStang

Engines that rev really high usually put out pretty decent hp/liter numbers. A v12 is going to be easier to spin up than a v8, simply because each individual piston is going to be lighter since there are 12 of them. That, and it is a very expensive motor.

3valGenIv

WARD'S AUTOWOLD had and article back in Oct 1, 2003 ,about GM working on a 3-valve-per-cylinder for the pushrod V8 and V6 ,that just about equal to dohc in RPM and HP but cost less to build. MR. Alan Hayman,Manager-advance concept group in GM powertrain's said that the 3Valve per cylinder for small block would be out after the Gen IV small block V8 is introduced. That was back in 2003 and the Gen IV is out, so it won't be long and we will start seeing and driving with 3valve per cylinder PushRod V8 and V6 engines in our cars and trucks!