Subject: Any ideas how to get a VW motor to put out the same HP?
Che Castro
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posted on April 17th, 2004 at 02:07 AM
it was only the SPG roller cranks that were pressed together without any locking system. I think other roller cranks like porsche ones locked to the
rod journals with a spline. The SPG ones often twisted out of true from drag race starts. Also the SPG ones would be stuck with the same set of
rods it's entire life. Research has also shown that plain bearings have less drag and longer life than roller bearings in a crankshaft application
Jon
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posted on April 19th, 2004 at 12:00 PM
Quote:
Originally
posted by 1302Steve
On the other hand no one can get near Gummleys supercharged type 4 powered hillclimb car, even when using twin cams, 16 valves, turbos etc.
1302Steve
Gumley got beaten a few weeks ago at the Victorian Championships. By an imported Pilbeam with an engine that I believe was handmade from scratch, I
think I heard the figure $30,000 mentioned. I dont know what the times were, but I know they were close, the pilbeam was on new tyres, the SCV on old
tyres and Pete was getting closer each run. Pretty good that a car built in a shed in wollongong can come close.
I dont think that 4 valves is the way to go. Not from any scientific engineering analysis, only by driving japanese cars. They have absolutely no pull
at low RPM. You have to rev them to get them to go, and the VW case doesnt really like to have a fast spinning crank inside it, witness the
tunnellboring machine hard at work matching all the main bearings to the flogged out centre main. The flat 4 configuration is ideal for producing
torque. Take advantage of that instead.
Theres a brand new Corolla in my driveway (babysitting for mother in law) at the moment. It just starts to pull hard at 4000 rpm when it starts to
sound harsh. I'd hate to hear it at the 6500 redline. But damn it sticks to the road. Its an easy 10kmh faster around my favourite freeway onramp
than my lancer. 20kmh faster than the kombi.
Chris.... kombi pilot, oval dreamer... finisher #26971 2005 city to surf
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posted on April 19th, 2004 at 03:55 PM
Corolla at 6500??bwaahahahaha it would only just be exploiting its cam timing by then. rev it to about 7500 and have some fun in it. An engine like
that will sit up there in the rev range all day with little ill effects!!!!!
Unfortunately, there is only certain amount of tourque to be had from a single gulp of air and fuel. (no blowjobs here)
Horsepower figures are really derived from an equasion of torque and engine RPM.
So, verrry simply put, if an engine can be made to produce the same tourque figure at so many hundred (or even thousand) RPM higher, it produces more
horsepower.
So to get 150BHP/litre even with the best indiction available it is going to take some very fancy induction work and in order to allow that engine to
rev enough to achieve that HP. Its going to have to rev it arsehole right off actually.
Single big valves are not conducive to very high RPM and dont flow so well at very high gas velocities, and require very high spring seating and
compression pressures to maintain copntrol at high RPM (valve bouncing) and due to this suck an enormous amount of HP just beign driven whereas a heap
of small valves are very light and will tolerate quite happily huge RPM's with light seating and compression spring pressuresand are better able to
actually allow the flow rates required to get the HP figiures/liter we are discussing.
Put quite simply, revs = horsepower (assuming the induction system allows the flow rates at those higher RPM.
This is exactly why your late model Jap multi-valve iron needs to rev to ear bleed levels to make the power it does.
The make such a good increase in top end that they feel like they have no low down (peaky) but you may probably find that RPM for RPM they are
producing still more go (torque) than a dak dak at the same RPM
An engine that pulls well down low at the expense of high revs Ie: a kraut, produces bugger all horsepower.
Bottom line is the only way to increase the tourque necessary to achieve 150Hp/litre without around 10,000 to 11,000 RPM is with forced induction.
Way it goes really!
L8tr
E
Im not a complete idiot, quite a few parts are missing....
Che Castro
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posted on April 19th, 2004 at 05:20 PM
4 valve engines can and do have low end, 2 smaller intake valves would have more port velocity than an equivalent large single one.
This graph plots the torque curves of exact same engine with 2v vs 4v
Also late model engines also benefit from a variable length intake etc. Variable valve timing/lift can let u have your low end and still have high
peak power. This also combines well with a turbo
And the comment about lack of pull in jap engines - I think wes would disagree
[Edited on 19-4-2004 by Che Castro]
Jon
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posted on April 19th, 2004 at 05:44 PM
Heeey dont make me sound like a bitch. I dont mean to say that they dont pull at all, I just think, from my own personal experience of driving the jap
engines is that the percentage of pull at low revs is minimal to what they have up high. The only exception I have driven is the VWRX notchback with
its first engine. That thing was like a tractor. Probably about the same peak horsepower as my fastback but it had it from idle to 7500.
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posted on April 19th, 2004 at 10:24 PM
Double overhead cams and 4 valves are an interesting topic. Basically, the main advantage I PERSONALLY :P see is that with bigger valves, you need
much, much, much heavier valve springs. 2 small valves need minimal valve return so therefore have less resistance on the motor.
My girlfriends new car is NA, has variable valve timing (fully variable cams), variable intake, hollow cams, etc, etc, etc... With full LA emmission
legal induction, noise and pollution. The bent 6 puts out 280BHP at just on 6000RPM. Coupled with very light flywheel, trick trans, carbon driveshaft
and so on the power is simply instantanious! Open it in any gear, any speed, any RPM and it puts you hard into the headrest and you stay there!
Granted it's not an SL55. But it also is Aluminium and only has two seats... Therefore considerably lighter than even most hatchbacks.
I also found out that all Japanese cars are, by law, only allowed to be sold with 280BHP max. However, we're going to Tokyo in a couple of months and
a trip to NISMO is being organised. Don't worry boys, I checked with the dealer and any NISMO parts and mods are still covered by Aus warranty
What does this relate to a VW motor I hear you ask? Well... The way I see it is; by the time my VW is on the road I reckon I'm going to need atleast
200BHP just to save face. Looks like going turbo will be mandatory :jesus
Che Castro
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posted on April 20th, 2004 at 09:02 AM
hehe sorry didn't mean to sound catty amazer. I do know what you mean though, lots of jap engines need their tits revved off them to get some power,
but i think they are usually in econobox type cars.
dad owns a late model Honda Prelude, its a H22A 2.2L Vtec. Pulls pretty hard from about 2500rpm all the way to about 8000rpm Vtec comes on at about
5500. peak power is about 200hp, and the buildup of torque is progressive and smooth as it spins faster (except when the vtec kicks in). The Vtec
thing is kinda silly how it suddenly kicks in, i think its more of a gimmick - other makes have similar variable valve timing/duration that changes
continuously.
I think maybe solenoid acutated valves might be whats next. If you need a different camshaft profile, you just upload it to your ECU There would be no parasitic loss to valvetrain friction, valve springs
etc. no valve float.
Jon
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posted on April 20th, 2004 at 02:21 PM
Yeah, I love the idea of solenoid actuated valves. BMW are developing a motor with them as we speak.
