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 pete wood
A.k.a.: figure itout
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 posted on May 15th, 2006 at 09:40 PM |
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Why were VW rally cars down on power compared to similar cars in the 70?
Over the last few years, I've been reading lots of stuff about the Porsche Salzburg 1302 beetle that rallied during the 70s. Everyone said they were
great cars and had amazing drivers, but the same thing keeps being said, "they were down on power compared to the rest of there class."
Why is this?
here is an article on the cars,
http://www.rallybugs.com/engtrans.htm
which reports they were getting 126hp from a 1599cc motor. good in my books. What do people think?
What is a good power figure to get out a 1600?
The reason I ask is that, I have a 1600 in my garage. I was thinking of building up khanacross special, but a PRC rally car might be a lot more fun
and street registerable too. To stay in the 1301-1600 class and be competitive, I was thinking of building a mental 1600 motor maybe with some EFI of
some sort as I have the type 3 manifolds.
What would be the specs then?
which heads? valves? cam? compression ratio? exhaust?
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68AutoBug
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| posted on May 16th, 2006 at 12:38 AM |
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Thats a lot of power from a 1600 beetle engine...
The Mitsubishi Lancers back in the 70s had 100 hp from their standard 1600 engines...
but what they got out of them from hotting them up I've never heard....
But it seems a lot more horsepower can be gotten from a water cooled engine, compared to a VW engine of the same size.....
I think its just the old design of the engine....
and I believe that a VW engine uses more fuel than a water cooled engine of the same horsepower....
Lee
- [size=4]Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY--- [/size]
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Doug Sweetman
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| posted on May 16th, 2006 at 10:41 AM |
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yep, 126hp is plenty from a 1600 - there would be very few NA 1600's around nowdays that made that number, thats for sure.
I think its more that they were racing against cars like BDA escorts and the like - which were more like 200 - 220hp.
Its all in the heads I think......
You should chase down a copy of Reinhard Kleins 'Rally Cars' book (mine cost me I think about $80 a few years back) - the most comprehensive book on
rally cars ever written. Has a couple of pages on the beetle.
good read.
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bus914
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| posted on May 16th, 2006 at 12:47 PM |
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| Quote: | Its all in the heads
I think......
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i think so too.
to get 126hp at the flywheel of a 1584cc you'd have to get each cyl to flow around 90cfm.
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pete wood
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| posted on May 16th, 2006 at 01:29 PM |
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well, these days we have much better heads available off the shelf don't we?
also, I just looked again at the site. It stated that the comp ratio was 9.1:1. Which they point out is quite tame. Surely between better heads and
more compression you could do better?
Toyota was getting 125kw out of their 20valve motors. I know that's alot more, and they rev higher, but surely we could do better than 126hp.
BTW, I doubt lancers were making 100hp standard. I had a 1600 galant and it was ok, but it wasn't that good.
BDA escorts were 2litres weren't they?
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koolkarmakombi
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| posted on May 16th, 2006 at 01:42 PM |
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The Cosworth BDA is a power plant that changed the face of rallying and racing after it was released in 1969 when it was fitted to the RS1600 Ford
Escort.
It was originally developed as a 16-valve DOHC conversion to the Kent 1600 pushrod motor for Ford UK. The basic engine type has been built as a 1098cc
unit taking it out to a 2137cc stroker. At its peak of development in 1986, it had evolved under Brian Hart’s expertise to be the BDT-E, a 2137cc
fuel injected, turbocharged engine that could produce a whopping 650hp. In the early 1980s, other derivatives of these engines were used in the
legendary Ford RS200 Group ‘B’ rally car, again turbocharged and injected in an 1803cc variant. For simplicity’s sake I will refer to this
family of engines as the BDAs.
One of the challenges facing the use of the BDA for racing has been the choice of engine and specification for the required application. While
capacity choice is fairly obvious, state of tune is not. If you are trying to shoehorn a methanol-injected 1600cc open wheeler engine into your Escort
you may be disappointed. A full race 1600 engine built for race fuel and with cams that come on song at 6500 rpm but pull hard to 9750rpm, can have
around 225hp.
This disclaimer does not reflect the thoughts or opinions of either myself, my company, my friends, or my dog: don't quote me on that; don't
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pete wood
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| posted on May 16th, 2006 at 02:58 PM |
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So what's the verdict? It'd need better heads? It'd need to rev hard? how hard then?
I can't just put it down to boxer engines, ferrari made great boxers. And it can't be an aircooled thing. There are lots of aircooled bikes making
mental power. It can't be a pushrod engine issue as there are lots of V8s making big power with only 2v/cyl and pushrods.
What's stopping the motor making the figures?
Added to that, how would you get good flow figures for a VW head of that size (1600cc)? Valve sizes? Porting style?
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pete wood
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| posted on May 16th, 2006 at 03:46 PM |
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| Quote: | Originally
posted by bus914
| Quote: | Its all in the heads
I think......
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i think so too.
to get 126hp at the flywheel of a 1584cc you'd have to get each cyl to flow around 90cfm.
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did some quick maths,
for 150hp you need 107cfm,
for 175hp you need 125cfm,
for 200hp you need 142cfm.
what does a stock 040 dual port head flow?
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Doug Sweetman
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| posted on May 16th, 2006 at 04:27 PM |
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I wouldnt guarantee that better heads are available now. From memory the heads on the porsche salzburg were some fancy semi-hemi cut with big port
work - no idea on the cam, but these also ran dry sumped. From memory they had a funny size twin weber setup - I seem to recall 46 IDA, but I'm sure
they were never made - its probably a misprint from 36......
Think about it as specific power output Pete.
126hp, 1584cc = 79.5hp/L - 60yr old basic design (now), 2V/cyl, 3 main bearing crank, 9.1:1 compression etc etc
Ferrari 360 Modena - 400hp, 3586cc = 111hp/L - extremely modern design, 5V / cyl, fuel injection, much better ignition system, modern intake / exhaust
and combustion chamber design, 11.2:1 compression.
If you could bet 111hp/L (for years the holy grail was 100hp/L for NA) from the 1584 that would give you 175hp. The only 1600cc NA engines that I can
think of that make this sort of specific power are engines like the Toyota 4AGE 20valve, which makes about 165hp or thereabouts. And that has quad
throttle body injection !!
I think the porsche salzburg guys did pretty well.... I'd guess they kept compression down to 9.1:1 to keep things relatively cool and for engine
longevity....
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bus914
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| posted on May 16th, 2006 at 04:35 PM |
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its also an efficiency issue as you wouldn't want to rev it past 8k. the heads need to be cut for mental compression. mental for aircooled machinery
standard for watercooled engines.
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pete wood
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| posted on May 16th, 2006 at 06:12 PM |
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mmm, interesting. I spose 126hp from a humble 1599cc motor is not bad considering it seems they were running stock crank and rods.
found this site.
http://users.erols.com/srweiss/index.html
has heaps of interesting figures on it. like these head flow figures...
http://users.erols.com/srweiss/tablehdc.htm#VW
can anyone interpret them?
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dangerous
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| posted on May 16th, 2006 at 07:18 PM |
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Lets just put this into perspective.
If this is the same "HP" as the one they invented years ago, then that is outstanding.
And not the Shetland pony kind of horsepower.
If your volksy had 126hp, and weighed 850kgs, it would run 96 to 97mph at the drags in about mid 13s.
So if that is poor HP, then all those 1915s and bigger that cant get faster than 16s better get them updated to '70s technology.
I don't know what pressure drop those flow figures are quoted at, but they are irrelevant unless the manifold and carb are
included (type 3 manifolds will kill flow), and my experience has shown that you will need to optimise the engine to achieve anything close
to the theoretical HP potential.
The general rule is the flow at 25" pressure drop is the potential power available in an optimised engine.
On a volksy with low comp and poor optimisation of intake and exhaust lengths, you may only see 100hp from the same head....but that is still in the
15s at close to 90mph.
| Quote: | Originally
posted by westi
That's mad Alan.
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pete wood
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| posted on May 16th, 2006 at 07:53 PM |
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I was hoping you'd wade into the debate Dave.
What sort of manifolds would do the trick then? How much compression could you safely run? 10:1? What would the heads and valves look like in terms of
size and porting?
Can you explain a bit more about how the flow figures work. What does 25"of pressure drop mean?
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BiX
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| posted on May 17th, 2006 at 01:20 PM |
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I think also it comes down to VW engine are restricted to 2 valves per cylinder, while most of the other 1600's where 4 in race spec.
I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!
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1303Steve
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| posted on May 17th, 2006 at 02:13 PM |
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Hi
Regarding the 46 IDAs, they were from a 904 Porsche, I used to run them on my 1302 before I went EFI.
I think its mostly in the heads.
I helped a friend with an old Volvo Penta, 2 litre Volvo car motor, pushrod, twin carbs, just like a 2 litre kombi. It looked like an Cortina motor.
It was rated at 120 hp. A 2 litre Kombi motor is rated at around 70 hp. The volvo heads were far better design than the VW kombi heads.
The thing that helped VWs in rallying was thier traction and durabilty on rough roads.
Steve
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VWCOOL
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| posted on May 17th, 2006 at 02:48 PM |
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Similar? What's similar to a VW?!:P
Keep in mind these were big dollar engines and as impressive as 120-ish hp from a 1600 is, attempting to replicate one might drive you nuts and make
you broke!
Steve is right, the Beetles' strength were that they were simple and durable (Larry Perkins built one for a Wynns safari years ago and nearly won
against factory Ralliart Pajeros et al!!) but as far as I know, never really set the world on fire
if you are reseraching a hottie engine for fun, maybe grab a 'bolt-in-and-go' package from an engine builder
[ Edited on 17-5-2006 by VWCOOL ]
Pay your debts, CxxT
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pete wood
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| posted on May 17th, 2006 at 04:13 PM |
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maybe I'll go back to the mid engined turbo khanacross special idea. I'm not really interested in a grenade.
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dangerous
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| posted on May 20th, 2006 at 09:17 AM |
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Pete,
The pressure drop is the term used to describe the size of the suck used to test the heads.
!0" pressure drop would be small and give a smaller number and 28" is a big suck and would give a higher CFM.
The engine does not have to be a grenade.
Building a smaller engine should cost nearly the same as a larger one as far as care and quality parts,
But a bigger engine will make the power easyer because of bore shrouding and reaching the
efficiency rpm point earlyer.
I can share some thoughts on a small engine combo (88x69) if you want, but a 94 bore engine
will open up alot more power because the off the shelf heads that are available suit these and the
end cost for more power will be nearly only the cost of the bore kit and machining (under a grand extra)
Will add more to this discussion when I can make the time.
| Quote: | Originally
posted by westi
That's mad Alan.
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rallydave
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| posted on October 8th, 2006 at 11:35 AM |
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HI all! hate to be a busy bee but I think you'll find the hp figures quote were flywheel and not brake hp.There are lots of homologation paper pics
and articles and pics on rallybugs. Compatitive vehicles of the time were?????? Rally cars of the EARLY seventies were quite simple with modest hp
figures(really good for VW)When ford introduced the Group 4 multi valve engine everyone now knows as the BDA the poor bug couldn't ever hope to
compete even with its excellent traction and lightness.The Austrian bugs were driven the way they were because even THEN they struggled to keep up!
You've got to make up time in the stage somehow,if the car won't keep up with you,you overdrive it!!!!:bounceand work upon its strengths.Drag blokes
find this part of our sport to understand. Most average bugs go out the traps at 70-80 mph?I'm still trowing mine sideways at 60mph... well ....In my
rally beetle 80 is about as fast as you would dare to go with it in the forrest.beetles do not hit trees very well .Hp isn't the ONLY thing in a rally car. Reliability,ease of
service,enjoying driving your vehicle for longer than 13seconds....but i will admit under the present production rally car rules even with the
freedoms allowed for pre 1985 cars,it's hard to make one air cooler stay together for over the first 100kms of FLAT out driving. Still, go and have some fun.
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Baja Wes
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| posted on October 8th, 2006 at 07:22 PM |
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| Quote: | Originally
posted by pete wood
Why were VW rally cars down on power compared to similar cars in the 70?
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Because the VW engine was designed in the 30's.
The early porsche engines started addressing the design flaws. The heads were one of the first area's of attention, they tilted the exhaust valve out
on an angle. This made a gap between the intake and exhaust valve for some cooling air to be able to make it through.
Of course OHC designs are always going to make more HP than pushrod designs, less valve train inertia means higher rpm for a certain valve spring
weight.
The air cooled design gives a relatively uneven combustion chamber / cylinder temperature distribution, which increases the chances of knocking
related problems.
If you want to look at how to make a lot of HP from a small engine, you need to look at motorcycle engines.
2006 Yamaha R1 (998cc) produces 175HP @ 12,500rpm.
They have big bores compared to the stroke (short stroke) to allow high revs. High revs = big HP.
Smaller engines have less inertia, and are easier to make rev higher. So smaller bike engines have even higher HP/L
2006 Yamaha R6 (599cc) produces 127HP @ 14,500rpm, which is about 212HP/L.
People mentioned the 4AGE 20 valve (165HP = 103HP/L) engine as being good power/size. Most poeple will know that yamaha designed the 5 valve head. For
good breathing you need the biggest valve area possible, and 5 valves gives just that. 4 valves is not far behind, and a lot of manufactures stick
with the 4 because the believe the extra parts for 5 isn't worth the small gain in valve area.
The old 2 valve VW head can never come close to the same valve area for a certain bore size.
So anyway, back to the main part of the topic. The VW engine just doesn't have the technology required to make the same power as the more advanced,
more modern designs.
[ Edited on 8-10-2006 by Baja Wes ]
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