I've got some pretty interesting dyno readouts of my 1880cc (90.5x73mm) engine & my 2027cc (94x73mm) engine. The only change I made when I rebuilt the 1880cc was switch to 94mm pistons to incease the capacity.
The hp was only increased slightly from 90.4 @ the wheels to 93.6@ the wheels, but where the power comes in is dramatically inceased.
And no, 94mm pistons do not run any hotter, my head temps & oil temps are the same as before.
regards
Jak

PS just a little foot note, 90.4 hp with 90.5 pistons, & 93.6hp with 94mm pistons, those numbers are a little weird huh??

.

I suppose you'll get a lot of

"I told ya so's"

More power and comes on earlier, although peak was reached a little later.

Good one Jak :thumb

Jeez Guys looking at those dyno sheets almost made me seasick when following the mixture curves or should I say waves.
:repuke

Without bagging anyone out or trying to sound negative those carbies really need to be sorted out if you are serious about comparing figures between engines or if you like more to the point comparing 90.5s to 94s a pretty tired argument I think in anyones books.

From memory I think mixtures should read somewhere in the ball park of around 12.5 : 1 for optimum performance. Having said that, cant wait to see what sort of power these little engines could produce as the numbers are very good in retrospect, always keen to see the VW performance people out there doing their thing in motor racing, keep it up.
:thumb

Yeh I know about the air fuel, but they were the same jetting setup for both, so they are a direct comparison.
Jak

Try about 1 size larger on both the mains and air correction jets. I'd guess there's another 5-10 HP hiding in your current setup.

Looking at those figures maybe I should build a 82X94 instead of a 82X90.5!

This is the tourqe readout as well. U can see the dip in the tourqe curve in relation to the hp curve.
I've got it on video that the tacho went to 6900rpm, & I'm pretty sure that it was taken from around 2800 to 3000rpm.

I'm definantly going to try the larger main jet & go from there. Wish I had a dyno in my garage.!

It's funny Brendan, I was actually going to suggest u go with the 94's to make 2276 as apposed to 2110cc.
I'm definantly going for the bigger crank once I get the air fuel sorted.

regards
Jak

Jak,
That's a big deal how the power and torque come on sooner. Any guess at the HP range for mine?
82X90.5
Twin 40 Dels
CB044s mild port job.
Engle 110

P.S. I will go to 94s when I build the 1776 for my daughter.

U would hope for 100hp at the wheels (but don't we all) but with that small cam it may just end up being a tourqe monster & run out of breath at 5000rpm.?
I can't guess anymore, but the dyno tells all, I suggest changing that cam for a K-8 with 1.4s..................but u knew thats what I would suggest.
Jak

Jak
Have you found out how to convert the torque curve to foot/pounds?I would be interested to see the difference between your 2027cc and my 2110cc

Cheers
Paul

No I havn't yet mate, but I suppose we just hold them up to the light..............
Can u take a digital pic & post it in here, i forgot to take a pic on saturday. Interstingly enough, he only took your car to 6000rpm on my video, wheras he took mine all the way to just shy of the 7000rpm porsche tacho. maybe the long rod verse short rod aspect is coming into effect??? Then there is the 3mm crank size difference as well.
I want 100hp at the wheels & apart from forced induction, after getting the mixture fully sorted, an 84mm crank is looking even more atractive, especially since my case has been CNC machined for it already, just open her up & drop it it.
Jak

mmmm,
82mm or 84mm and some CB Performance CNC ported heads are also on my wish list!!!
One day , maybe

Just rolls off the tongue doesn't it ...84X94.

The 110 cam will also go into the daughter's 1776 so a K8 and rockers will definately be on the shopping list.

BTW car is now on all 4 wheels!!

I can convert the torque if those RPM points are correct.

the two rpm markings on the graph don't match each other. Are you sure of the 2800 or the 6900?

Jak,
Not sure if a pickup for RPM was connected to the cars. You might need to do some calculations with wheel diameter, final drive ratio (or the ratio of the test) and apply it to the KPH reading along the bottom axis of the graph to get the RPM reading.

If you don't use the pick up on the dyno dynamic machines it can be set manually using a ratio ... run the car to a certain speed cheek the revs thru the car tacho (or one attached) then tell the dyno the speed and revs.... then it gives the engine rpm...

Here's the chart assuming the 6900rpm @ 127.5kph is correct.

Thanks very much for that Wes, most appreciatted, the 6900rpm is definantly correct as I have cross referenced it with the video, but the dyno operator holds it just below 3000rpm before giving the final run through the revs.
regards
Jak

Just gotta ask - what cam, heads and carburation you running, jakriz? I was just pokin' back through the messages and saw something is choking your engine past about 5-5.5k. (probably head-related, but it could be carbs.)

And I gotta add: Your comment that 94s don't run any hotter because you have oil and head gauges isn't very scientific. An engineer worth a pinch of snot (not the very mouthy one that gets around here,) will tell you that 94 vs 90.5 will run hotter (try an infrared spot sensor on the cylinder surface,) it's pure maths: increase in energy throughput and friction (in the larger swept surface) and decrease in surface area available for disspation will mean the cylinder and piston will be running at a higher temperature. The question is: how will this effect the performance and longevity of the engine?

Piston and cylinder technology have come a long way since Gene Berg died. But I'd still like to see a back-to-back comparison of leak-down figures after, say, 40,000km before anyone claims there aren't heat problems with 94s. Drag racers don't make such claims, but they do work _with_ such factors.

94s are supposed to run hotter because of the thinner metal in the cylinder compared with the original cylinder..
unless the cylinders were not made by VW and the thickness is the same, allowing the heat to disperse the same...
Lee

Forget the theories , scientific calculations etc etc, I've just done a back to back test with 90.5 to 94 & I've done 3 Supersprints this year with the 94s, not just posing around the street & daily driving to work, how does 4000rpm to 7000rpm for 10 laps at a time sound. I'm far from any scientist, but making only a piston size change & then heading back out to the track for some racing will beat anything u will read in a book any day of the week.
My good friend John who also races has had the same 1916cc together since 96, daily driven to work & also does 9.6seconds on the 1/8th mile! Tell him that 94's don't work for a long time.
That aside, why do u think that the engine doesn't pull past 5000rpm? It didn't make full power until 6500rpm, the heads are 040's with 40x35 valves, ported by Richard Holzl, tall straight shot manifolds that have been match ported, dual Berg springs, Berg 1.4 rockers with a Steel Billet cam in the K-8 grind, 555thou lift with 298duration. The heads probably are restricting it & I have a set of 044 magnums with 42x37.5 valves to go on at the end of the year. Maybe I'll get 100hp at the wheels then?
regards
Jak

Oh & the carbies are 45mm Dellortoes with the CB Performance update kit (horizontal discharge tubes) , I've also just yesterday the standard fuel pump for an electric one & have already noticed a little more pep throughout the entire rev range. I'll try & get back to the dyno next weekend before my next event at Eastern Creek .
JaK

Autostik, you need to get realistic. The difference in temperature your talking about isn't worth knowing about. Changing the ambient air temperature by 1 degree is going to have more of an effect than what you are talking about. If you were an engineer, you'd know that.

Jak's head and oil temp sensors are just fine. The head temp is the main one to worry about and he monitors it.

Lee, 94's are not thin walled. They are thick walled cylinders just like stockies.

I guess people can listen to people that sprout out strange theories with no practical experience, or they can listen to Jak that has actually tried more than the rest of us. I know I'd be listening to Jak.

What he said :thumb

As much as I have respect for the Bergs. Apparently their 94vs90.5 tests were done something like 25-30 years ago :o
Nothing improves the breed like racing. Sticking a car on the track will prove it everytime. Just ask Motor magazine about the HSV's at Winton. A couple of laps and they were all pissing fluids and "feeling like half a million kay taxis"
Daily driven and raced is enough proof for me.
This is being discovered by alot of tuners in the last couple of years. Everyone was so scared by what Berg said they've only just gone "stuff it, lets try break 'em" (has been happening on shoptalkforums alot lately) and finding theres no difference except for better performance. The 92 and 88 thin wallers are still unreliable, but thats another matter all together.

[Edited on 6-10-2003 by Cam]

Thanks for the intelligent and honest reply Jakriz. I wasn't trying to attack 94s, simply pointing out that some people look in the wrong place for possible effects. Past information from people such as yourself completely changed my opinion of the current viability of 94s - technology has come a long way in the past 30 years and running 9s in any street-driven car for any length of time is pretty impressive.

My needs are a little different due to where I live, however, and I'm sticking with the 90.5s until someone produces some evidence that I can get the life I need on lots of long hauls - I pull more k's in a year than most do in the life of their car...

As for saying it's not pulling past 5000, have a look back. I said it seems a little "choked." I suspect, as you do, that the ports are holding it back from it's full potential. There's only so much the best porter in the world can get from an 040, that's why CB invented the 044...

Once you've done that, you may find that you've surpassed the abilities of the 009 (please don't tell the True Believers I said that,) and look at the MSD. Back in the days when we couldn't get things like the MSD at a realistic price, we'd fit slightly stronger springs to the 009, or whatever, to move the curve a little further up the range; then increase the static advance as much as we could again.

Little gain in power?, C/mon Ben, your more experienced than that, look how much fatter the power line is. I've got the lap times to prove it as well, I took 2 seconds off Oran Park short, 4 seconds off Oran Park lon & 2 secinds off Wakefeild, yet to do Eastern Creek again. & for the first time I can keep up with CT in a straight line & we are using the same gearbox. With the 90.5's (1880cc) I just couldn't stay with him on the straights.
Proof enough for me
Jak