- 1,103
- Cribanox
BIG UPDATE
Can a mod sticky this? I am adding this edit to make it easier to fidn info
Here are some good points, info, quoted from inside the thread.
(All I did was used 10 minutes to scroll through and copy/paste some interesting points after i skimmed over all the pages, sorry if I missed anything good.)
Duke
Famine
Duke
Famine
Taurine
Daggoth
Famine
Ghost C
Retsmah
Firebird
retsmah
vipergtsr01
Slicks
inferno
slicks
Thecracker
///M-Spec
Famine
Firebird
Azuremen
KurtisGSXR
END OF BIG EDIT
I'm still on my never ending information quest about cars , motors, and etc. I have come across a few questions that I'd like answered, so, thanks in advance 👍
1. How can you tell what kind of Turbocharger can fit / be used to potentional on a certain motor? Or if it can even fit? Keep in mind I don't know what the specs on a turbo charger mean.
2. What does the liter amount on an engine do for it? My car only has a 1.5, and I hear of cars that have more than double that.
3. What do cams do? I've heard this many times, "You need overhead cams", and I always just shrug and say "huh?"
I'll have more some other time, thanks again fellahs.
Can a mod sticky this? I am adding this edit to make it easier to fidn info
Here are some good points, info, quoted from inside the thread.
(All I did was used 10 minutes to scroll through and copy/paste some interesting points after i skimmed over all the pages, sorry if I missed anything good.)
Duke
Litres or cubic inches are the displacement of the car's engine. This means the volume of air/fuel mixture that gets drawn through the engine in one complete cycle with all cylinders going through their intake/fire/exhaust cycle.
Cams (short for camshafts) are a long shaft of steel with a series of irregular egg-shaped lobes on it. This shaft rotates with each motion of the engine, and the lobes are what open and close the valves in each cylinder at the appropriate time. The cams and the crank shaft (which is what moves the pistons up and down) are coordinated by the timing belt or timing chain.
Famine
Pushrod <- SOHC (Single Overhead Camshaft) <- DOHC
It's true!
OHC engines are more fuel efficient and are capable of both more torque and more revs than pushrods. DOHC allows four valves per cylinder (I believe pushrods CAN get 4v/cyl but require quite a bit of jiggery and indeed pokery to do it) which means it can do the same but even MORE so.
DOHC rules.
Duke
Originally Posted by Famine
Except the PPP chip (an OFFICIAL OEM product) screwed my brother's Impreza RB5.
Be. Careful. With. Chips. (End of famine's post, beginning of duke's)
Then there's the Venom 400 reprogramming for the Neon, which costs about $400 and is basically a sticker they put on the outside of your engine controller. After people figured that out, they brought out the Venom 500 which cost $400 and made your engine run worse.
Not to say all 'chips' are bad - I run a Mopar Performance ECU in my Neon that was ~$300 and made a serious dent in my accleration times - but they are no magic bullet, particularly when programmed by people who don't know what they're doing.
Famine
Slick Rick - PPP = Prodrive Performance Pack. Created, designed and installed by Prodrive, Subaru's official European "aftermarket" (or occasionally factory) modifier. Who also make the rally cars for them.
For crying out...
Subaru supply the base car to Prodrive. Prodrive do the modifications. Prodrive send the car BACK to Subaru who then sell it as new.
His car was a Subaru Impreza RB5 PPP - that's a Subaru Impreza with FACTORY Prodrive Performance Pack. The PPP includes an ECU upgrade, amongst other things. Everything was factory standard. It was the same as the other 441 RB5s on the road. But, after several expensive faults, the diagnosis was that the chip - that's the ECU upgrade from Prodrive which was standard on the car AS supplied by Subaru FROM new - was faulty and had caused a cascade failure of electronic systems. Which, on an EFi car, is bad.
The chip was faulty. Official.
This was a STANDARD part (albeit a STANDARD part which was an upgrade over the "base" model's STANDARD part). And the STANDARD part was faulty, causing myriad other electrical faults. The point being that if a STANDARD part can screw your car up that badly, an aftermarket one can certainly do as much damage.
Hence the tagline:
Be. Careful. With. Chips.
Taurine
A valvetrain in a pushrod engine has more moving power-taxing parts then a OHC engine does.
I don't really see the harm in chipping (or going piggy-back) your ECU, of course bearing in mind that the chip alters the standard timings cycles and whatnot, as long as the chip doesn't change anything too drastic there should be no problem.
Programmable ECU's are where you need to know what you're doing.
Daggoth
There are two disks that link the engine to the transmission of the car. One at the end of the engine, another at the beginning of the transmission.
The disk located at the end of the engine is where you get the RPM reading. (again I don't know the name in English for this disk)
When you release the clutch and have a gear selected the two disks are pressed against each other and the car begins to move! That is why you need to rev up a little when releasing the clutch, you feed a little more strength in the engine so that it can move the car. If you don't rev the engine, the transmission gives to much resistance to the engine and it stops.
Naturally these disks have a limited life, specially the clutch disk, what is happening when you realease the clutch is a slide-grab situation between the two disks and the car starts to jerk! When the clutch is fully released and the car is in motion the pressure is so great that even with a worn-out disk the car won't jerk.
So, when you release the clutch this happens:
slide-slide-slide-slide-grab-slide-slide-slide-grab-grab-slide-slide-grab-grab-grab-slide-grab-grab-grab-grab-grab-grab
Each time it grabs you feel a little jerk.
I hope that wasn't to much confusing (and sorry for any typos or mistakes)
You should consult a mechanic! He'll tell you right away if it is indeed a worn out clutch disk!
Famine
They can't do much else other THAN torque. Get to 6000rpm and the valves start floating.
WHY the Corvette needs a 5.7 litre pushrod V8 to get 400hp when the same can be acheived with equal - if not better - reliability and efficiency from a 3.6 litre DOHC V8 is beyond me. Yes, you WANT that V8 sound and a DOHC V8 has a different sound compared to a pushrod one (comparison - TVR Griffith. Ferrari 430) but other than that there isn't a single sound mechanical reason for a large capacity pushrod next to a smaller capacity DOHC.
Incidentally, I'm led to believe that the Australian V8s - which are sourced from American Ford and Chevrolet V8s - are converted to DOHC from pushrod for precisely this reason.
DOHC/SOHC CAN generate more power and more torque, more efficiently and more reliably per unit displacement than OHC. Just because some manufacturers choose not to take advantage of the more power/more torque in specific applications doesn't alter this pretty fundamental principle.
Why do Ford Australia and Holden take OHV engines from their American parent companies and turn them into OHCs?
Why do European and Japanese manufacturers - where reliability, efficiency and package size matter more than outright power - use exclusively OHC engines?
Answer to both: DOHC/SOHC CAN generate more power and more torque, more efficiently and more reliably per unit displacement than OHC.
Ghost C
a DOHC setup weighs more than an OHV setup. Four cams as opposed to two, more weight. Twice as many valves, valve springs, etc more weight.
Retsmah
Pushrod engines have their advantages and disadvantages. A pushrod engine is more efficient when it comes to space... at the last autoshow Toyota had one of their 4.7l DOHC V8s on display, it's significantly larger than a 5.7l GM motor. In trucks this really isn't a big deal, but in sports cars where underhood space is often limited it is. All of that added weight goes on the top of the engine too, not where you want it for a low center of gravity.
To resond to something said eariler, there is no reason that a pushrod engine can't have four valves per cylinder, or be high revving. My Honda has a pushrod engine, which is also a 4 valve/cylinder design and revs to 10,000rpm. It's actually got a higher redline than the SOHC engines that Honda was building at the time.
A twincam pushrod engine has, as far as I know, never been done. That would require some fancy pushrodding... I'm sure GM could do it, but there's probably not any good reason to.
I think the bottom line is that there are some people than you will never be able to convince that pushrod engines aren't necessarily bad, and there are people on the other side too. The valvetrain, like everything else on a car, is a compromise between several different factors, in some cases a pushrod engine may work better.
Firebird
Power (in horsepower):
Dodge Viper SRT-10: 500
Ferrari F430: 483 (SAE)
Chevrolet Corvette Z06 (2004): 405
Chevrolet Corvette (2005): 400
Ferrari 360 Modena: 400
Ford Mustang SVT Cobra: 390
Jaguar XKR: 390
Maserati Coupe GT: 390
Chevrolet Corvette Coupe (2004): 350
BMW M3 Coupe: 333
Nissan 350Z: 287
hp/L:
Ferrari F430: 112.3
Ferrari 360 Modena: 111.1
BMW M3 Coupe: 104.1
Jaguar XKR: 92.9
Maserati Coupe GT: 92.9
Ford Mustang SVT Cobra: 84.8
Nissan 350Z: 82.0
Chevrolet Corvette Z06 (2004): 71.1
Chevrolet Corvette (2005): 66.7
Chevrolet Corvette Coupe (2004): 61.4
Dodge Viper SRT-10: 60.4
Fuel economy (Transport Canada figures in miles per Imperial gallon; they'll seem inflated to American forum members because Imperial gallons are larger than US gallons. All have 6-speed transmissions. All manual, save for the Jaguar):
Chevrolet Corvette (2004): 23 city/37 highway
Chevrolet Corvette (2005): 21 city/37 highway
Nissan 350Z: 24 city/34 highway
BMW M3 Coupe: 19 city/31 highway
Ford Mustang SVT Cobra: 20 city/29 highway
Jaguar XKR: 19 city/30 highway
Dodge Viper SRT-10: 14 city/26 highway
Maserati Coupe GT: 14 city/22 highway
Ferrari 360 Modena: 13 city/21 highway
Ferrari F430: 11 city/21 highway
Annual greenhouse gas emissions (in tons; from US Department of Energy):
Ferrari 360 Modena: 15.0
Ferrari F430:14.7
Maserati Coupe GT: 14.1
Dodge Viper SRT-10: 12.8
Jaguar XKR: 10.8
BMW M3: 9.9
Ford Mustang SVT Cobra: 9.8
Chevrolet Corvette (2005): 8.9
Chevrolet Corvette Coupe (2004): 8.5
Nissan 350Z: 8.5
Chevrolet Corvette Z06 (2004): 8.5
Environmental Protection Agency emission standard ("----" meaning not high enough for LEV certification):
Ferrari F430: LEV
Chevrolet Corvette (2005): LEV
Ferrari 360 Modena: LEV
Chevrolet Corvette Z06 (2004): LEV
BMW M3 Coupe: LEV
Chevrolet Corvette Coupe (2004): LEV
Dodge Viper SRT-10: LEV
Jaguar XKR: LEV
Maserati Coupe GT: LEV
Nissan 350Z: LEV
Ford Mustang SVT Cobra: ----
Evidently there isn't a single sound mechanical reason for a smaller displacement DOHC next to a large(r) displacement pushrod. The four pushrod engines above were as good or better as the supposed "high-tech" Ferrari engine.
Incidentally, I'm lead to believe you don't quite know what Australian V8s you're talking about (there hasn't been a single Ford or GM engine reworked from OHV to OHC by their respective Australian subsidiaries).
retsmah
pushrod motors are not limited to two valves per cylinder.
vipergtsr01
The Ford 4.0L was a single overhead 2 valves per cylinder design intill the current BA model where the made it a DOHC 4 valve per cyl engine, I am pretty sure the even eariler versions of this engine were push rod designs, I think Ford switched to OHC in 1988.
Also note Ford Australia dicthing the OHV 5.0L in replace for their 5.4 DOHC, problem is my boats Big Block chev engine is smaller that it due to the gigantic size of the heads.
Holden also has recently switched to DOHC now also with thier 3.6L Alloytech V6 engine.
Slicks
One point that none of you have brought up is engine longevity. Many pushrod engines (large V8's in particular) are relatively understressed engines. A low-stress engine (Say, a 405hp 5.7L V8) will far outlast a 3-4L, 400hp high-stress Ferrari engine under similar conditions. Or a Ford 4.6. Or a Nissan VQ-series engine.
There are many pushrod engines (Chevy 5.7 and 3.8 in particular, because of their widespread use) that have many, many miles on them. There is one documented 5.7 with over 1,000,000 KM on it featured on Motoring 2004 (Canadian TV show). And there are probably more that are undocumented.
Pushrod engines are simpler, and thus easier to fix. There are generally a wider variety of parts available to the pushrod engine (350, etc) at cheaper prices. They also have far more tuning potential. There are many more 600+HP smallblock Chevys running around than anything else.
Furthermore, guess what engine configuration is used in the vast majority of professional drag racing cars? Pushrod. I do not know of a single _OHC engine producing the 8,000HP of a top fuel dragster. They are all pushrod.
In fact, I challenge anyone here to find a NON-OHV engine (excluding aeromotive applications such as turbine) producing over 2,000 hp.
inferno
No much difference really. I've at least had the privalage of driving a variety of engines if not owning any. From the 4.0 liter OHV V6 in my dads ranger, to the 2.2 liter SOHC I4 in my moms accord. Also a jeep wrangler with it's 4.0 liter inline 6, OHV I belive, A nice 3.1 liter OHV V6 in a no longer possesed, Buic Regal and my little cuarberated, SOHC 2 valve pulsar. the one thing I can say is that both the Ranger and wranglers OHV engines dont like to rev. You get alot of vibration if you wind either of them past 4000 rpm. As for throtle response? no diference from the accord to me. Their is alot of extra oscelating weight and friction their with the pushrods, rocker arms and whatnot, but most SOHC 4 valve engines use rocker arms too and after you go adding in the extra valve springs, and stuf for twice the number of valves, power losses to the valvetrain would probably be very similar. Unfortunately the pulsar was carburated so natuarly it's throttle response sucked, and i cant do an unbiased comparison of OHV 2 valve versus SOHC 2 valve. the one stand out from the group however is the 3.1 liter OHV in the regal. that thing was down right snappy. Excelent throttle response, better than all the others and it didnt mind revving either. Plus the muffler was gone so it sounded sweet. God I wanted that engine in something with 2 doors. But back on topic. I attribute the dislike of revving more to the size of the big ford V and jeep inline sixes rather than the valvetrain. That being said their was never a need to go past 3K rpm with either of them. sorry for the essay
slicks
The throttle response of an engine would depend more on the intake system than on the valvetrain. A carbuerated engine with a poorly tuned carb will likely result in poor engine response. A properly tuned carb will give fast response, and fuel injection the fastest.
I doubt that a difference in valvetrains (between OHV, OHC) would make a difference in response. However, a OHV engine with rollerised valvetrain would likely be faster to respond than one with a non-rollerised valvetrain.
Thecracker
Top fuel dragsters are a crap comparison because guess what? - they run on 'top fuel' ie Nitromethane not pump fuel.
Dragsters that run in the 'pump fuel' classes have outputs of no more than 1350bhp - from 8.2ltrs
A Formula 1 engine has an output of around 950bhp (a conservative guess) from 3ltrs
Theoretically a 8.2ltr F1 engine would output 2600bhp on pump fuel. Thats without Turbos or Superchargers.
They just don't bother producing huge capacity OHC engines because they can get the same power from a lower capacity.
///M-Spec
Pushrod (OHV) Pros: compact, relative simplicity
Pushrod (OHV) Cons: comparatively poor high RPM performance, is variable timing even an option?
(D)OHC Pros: good high RPM performance due to more valves and better positioning of the valves, variable valve timing easy to implement
(D)OHC Cons: packaging, complexity
Despite my personal perference to own cars with DOHC engines (I like the high end power delivery and mechanical noises that comes with it), I don't think anyone in his right mind would critisize the LS2 V8 for being a bad design. Despite the 6.0 liter displacement, it is a light, compact and simple engine that makes a lot of power.
If you compare the LS2 to the S54 in the BMW M3, you'll notice while the LS2 is wider, it is shorter in height and length. You will also notice the LS weighs almost the same as the M3 motor (they are less than 50 lbs apart), yet makes a great deal more power (400 vs. 333). These are in comparatively priced cars.
(If anyone has weight and size info on a Nissan VQ 3.5, I'm very interested in seeing it.)
I don't you know about you, but "power per liter" doesn't have any consequence to me in a performance car. It doesn't DO anything. I don't drive "power per liter".
To me, the ONLY things that matter is power output (specificly, the shape of the torque curve), how much the engine weighs and how it room it takes up; fuel efficiency and reliablity being secondary concerns. Well it needs to sound good too, but I digress.
That being said, I fully acknowledge that in many countries, cars are taxed based on displacement. Therefore while specific power is fairly meaningless to me, it may be very meaningful to someone in another country.
Perhaps that is why the Japanese and Europeans seem to have "a thing" for specific power.
The second thing I wanted to say was that the Ferrari F430 vs. GM Gen IV V8 comparison is not very useful. No one is taking price into consideration; you can buy almost 4 C6 Vettes for the same price as an F430. Price independant, sure the Ferrari's motor may be superior, but when was the last time you bought ANYTHING price-no-object??
Now that I've made it clear my admiration of the GM Gen IV V8... I'm hoping someone can explain to me why the 3800, OTOH, is such a weak turd.
Famine
There is only one mass-produced OHV car left - the Ford Ka, using a 1.3 pushrod with origins in the 1963 Ford Anglia. This also happens to be one of the cheapest cars on the market and is often praised for its handling, but criticised for the lacklustre engine.
In addition to my Mazda example, Honda have never had a VTEC - OHC - engine failure on an engine within normal service schedule. Ever.
GTChamp2003 - No. A car isn't limited to "x" speed by its engine power. It's limited by its wheel power (along with frontal area and coefficient of drag - but we're assuming them to be identical). The wheel power from two 250hp engines would be the same as the wheel power from one 500hp engine, assuming, as you said, transmission losses are identical and allow identical wheel power.
Right now the sample size is very small indeed. Or "one" as it's known. 10 years ago there was a much larger selection, but the manufacturers - including Ford - have, one-by-one, dropped OHVs from their line-up. In fact, 10 years ago, Ford's reliability was nearly rock-bottom. Today the Focus is the most reliable car sold in Germany and their reputation is through the roof. Yes, other things have changed too other than JUST the switch to OHC, but it is interesting, at the very least, that Ford's European reputation has increased as they've gradually phased OHV out and that no OHV car in the last decade has placed in the top half for reliability OR customer satisfaction.
Firebird
Azuremen
The version in the Corolla GT-S is setup, in the US at least, for 180 HP. The Corolla XRS is setup to have a little more low end torque, as its still a Corolla. The result is less torque at high RPM, and thus a little less peak HP. Also, I think Toyota did not want to do out do their Celica GT-S by making a Corolla with the same power output in the US.
KurtisGSXR
Hi,
I'm a relatively new member, but I thought I'd offer a bit of knowledge on the OHV v OHC debate. Although this thread has meandered a touch to different subjects, the core discussion appears to be which is best.
I work for an automotive OEM and which is the best layout depends on a huge number of things.
The reason a lot of US OEM's use OHV, still, is probably due to a mixture of cost (why would you spend a few hundred grand on a single new HP diecasting tool just to have OHC?), familiarity with the design and concept, experience in designing the pushrod system, and market and brand awareness. And to be fair, although I'm a brit, I still love the noise of a big OHV US V8.
If however, you were limited as a designer to a specific engine configuration and size, for racing homologation for example, unless you HAD to work modifying an old engine to save costs, you'd go for DOHC. You get a much better included valve angle from OHC's in general (it's possible to get a 25 degree on OHV, but the packaging is a nightmare.) and much better volumetric efficiency due to the greater valve area. This is assuming an OHV with a 2 valve head, although they don't have to be, but packaging is a nightmare again.
If you were going for all out power, you'd go for DOHC. Again, assuming a max capacity. Better volumetric efficiency will give you a better torque output.
Thermal efficiency will be affected by the valve train to an extent, but it is more heavily affected by the quality and homogeneity of the fuel mixture, compression ratio, and the valve and spark timing. Thermal efficiency relates the amount of useful energy (kinetic) derived from your fuel's chemical energy. Typically about 35% for unleaded, 40% for diesel. No commercial IC engine in the world can get much past about 50%. Even then it's a marine two stroke diesel, a million foot pounds at about 102 rpm, nice, just what you want in your race rocket...
There is a huge amount of variables to take into account, and I can't cover them all, because I don't know them all. All I can say from my perspective is that every new engine we've designed in the past 10 years has been DOHC. Whether it's been for a sports orientation, or cruising, workhorse, whatever, they are all DOHC. For us it would be a marketing mess to have the word "pushrod" in a press pack, but for a 'vette or mustang it's probably the other way round.
thanks for reading, and if I'm wrong, let me know, I'm always trying to learn.
Kurtis.
An engine's power output is a balance of internal friction against it's power production.
Any engine, even the best has a huge amount of internal friction. The pistons, rings, bearings and pumps all feed off the engine power. When an engine is running in it's desirable speed range it easily overcomes it and produces buckets of grunt for us to play with.
As an engine revs higher, the mass of the pistons, rods and valve train all needs accelerating faster, requiring more power. There will come a point where due to valve timing, fuelling, many other reasons and the overall engine architecture, the amount of power required to turn the engine increases at a faster rate than the "theoretical" power output does. This means the power drops off. And it does it at an exponential(ish) rate, dropping faster the higher you rev it.
The rev limit can be raised by reducing the engine's oscillating and rotating mass, or reducing the stroke and increasing the bore. The reduction in stroke reduces the acceleration of the pistons and valves, using less engine power.
Kurtis.
The reciprocating mass does contribute a lot. But it is a dual edged sword. A lot of motorcycles are coming out with heavier cranks, when typically year on year they were becoming lighter. this is to improve drivability. A low inertia engine has a fast, agressive throttle response making the bike difficult to ride. I would think the property would be much reduced in cars due to the inertia of the flywheel and drive train.
Although it varies greatly from engine to engine, a typical spark ignition engine can have a peak cylinder pressure of 40-70 atmospheres, which is up to over 1000psi. Diesel engines are higher still. The highest pressures in an engine nowadays are not in the cylinder though. Modern diesel engines have fuel pressures of up to 20,000psi.
And I would agree power isn't everything, I like torque. Specifically low range torque. This is because I'm a lazy driver and I drive slowly. My bike is for riding fast, I don't want to have to work hard in my car too! So personally I'd go for an auto box and a nice quite ride. With a seat which gently cradles me like a lover...
Ahem...
Excuse me.
END OF BIG EDIT
I'm still on my never ending information quest about cars , motors, and etc. I have come across a few questions that I'd like answered, so, thanks in advance 👍
1. How can you tell what kind of Turbocharger can fit / be used to potentional on a certain motor? Or if it can even fit? Keep in mind I don't know what the specs on a turbo charger mean.
2. What does the liter amount on an engine do for it? My car only has a 1.5, and I hear of cars that have more than double that.
3. What do cams do? I've heard this many times, "You need overhead cams", and I always just shrug and say "huh?"
I'll have more some other time, thanks again fellahs.
