Engine works, but can it be optimized? Or maybe a new one?

[qubek]

It’s not really a topic for a racing forum, sorry, but I hope to get more technical replies here

The situation is like this: I have an engine that was assembled from off the shelf parts using some common knowledge from internet forums and some advice from my friends. The engine works well, I made few thousand km with it during the last season and I’m quite satisfied. But browsing through the topic describing Johannes Persson’s engine I was impressed with what you can achieve out of a VW engine when you have knowledge, experience and when you try to think and compute instead of just doing what other people do (like I did). Now I don’t wish to achieve 100KM/liter but maybe I can improve my engine somehow and obtain more than 54?
Please note that I don’t think about building a “sharper” engine (maybe I should?), but more about improving the combo, eliminating bottlenecks and things like that. My first thought was to rise the compression ratio, as what I have now is rather low, but I wouldn’t like to suggest anything, I'm interested in your opinions

The engine combo is like this:
Stock case
Stock crank, stock flywheel lightened to 5,9 kg, 8-doweled and balanced
Stock length SCAT I beam con rods
Mahle 94 p&c
0 deck height, 0,04 copperhead cylinder head gaskets bought from CB
043 heads with 40x35,5 valves. Bought from scat. They are unported, except for the area behind valve seats, which are blended. There is no step
Static compression ratio is around 8,9:1 – 9,0:1. I don’t remember the chamber volume, but it must be around 54 cc’s. I measured that and calculated the compression ratio some time ago and I can’t find the notes, I just remember the end result
C-45 Scat camshaft, stock 1,1:1 rockers
Melling 30 mm oil pump
Dellorto 40 DRLA with 34 venturis
1 5/8  VWspeedshop sidewinder copy
103KM@560 0rpm, 149Nm@~4100 rpm

http://img547.imageshack.us/img547/9042/pomiar1.jpg

http://img217.imageshack.us/img217/851/pomiar3.jpg



Or maybe I should let it be?

[Harry/FDK]

What carbs are you using now ?

[qubek]

Dellorto 40 DRLA with 34 venturis

[Harry/FDK]

Sorry, didn't read to well. It's a nice combo. IMHO there is HP to be found in the heads, rockers, maybe ignition and re-jetting of the carbs. But there's a ton of information together with very experienced engine-guru's overhere wich i'm sure they can give you lots of (better) advice. Good Luck !

[Zach Gomulka]

Very large gains can be found with proper porting, that along with some 1.25 rockers would really wake your engine up. The exhaust is a little on the large side, IMO, but not too far off.

[qubek]

Very large gains can be found with proper porting, that along with some 1.25 rockers (...)

As I said, I didn't want to suggest anything, but you mentioned it:

This is a comparison between my engine (blue) and one that belongs to a friend of mine (orange):

 
The difference is that he had his heads ported last season and he has 1.25 rockers, just as you said.
Of course, this is just a hastily made xls graph, comparing results from two different dynos, and there may be other differences. But it seems to prove what you say - you can gain extra hp by that.
The thing is that this gain is only at the higher revs. That doesn't mean that it's not worth it, this engine is not for a Bus 

[Fiatdude]

Reding your post -- I gather you are wanting better fuel mileage -- first thing I would do is remove all the interior out of the car (carpet, seats, windows, radio, speakers, spare tire, jack, etc.) put in 1 ultra lite seat for the driver and that should be good for about an additonal 5-10 km per liter.

[qubek]

I gather you are wanting better fuel mileage

Fuel mileage?    No, not really.
What I meant is that this engine, even improved, will not be powerful enough for proper racing. But this does not mean that I will not race.

At the moment I'm hesitating if I should drive it as is, or remove the heads and try to make it better. Hence my questions - can it be improved without changing the combo too much, how, and what can be achieved?
I know that this is not easy, but there are few people here who seem to be really good in calculating things like that.

[Zach Gomulka]

You may also be able to raise compression ratio at the same time, depending on the quality of fuel you can get in your area. Your venturies are a little on the small side, a CB update kit for the carbs will improve flow and up the venturi to a 36mm (I think).

[drgouk]

Why do the torque and hp lines cross at 4800 something? and not 5252?

[Torben Alstrup]

Hello.
Question is, do you want to take it apart and swop the crank ?

That combo can easily be tweaked (still on 69 stroke) and get up in the 135 hp range. But for a street car I would never do it on a stock crank. Not even a well balanced one. When reved high for longer periods of time, as on the freeway, the case WILL get pounded and have a short life. Racing bursts is a different game.

That said, you can increase the CR to 9,6 and get the heads reworked to something that matches a 1914. Going "Panchito" style wouldnt be bad.
Especially when the header is on the large side, I have had very good luck with reducing lift on the exhaust a tad with that cam. Over time I have found some stock style 1,25 rockers that actually lifted 1,3. I use these on the intake and stay with the 1,25´s on the exhaust. That REALLY helps the engine to bleed torque. Usually I get round 100 NM/ liter and at a nice and wide band.

Last year I built a couple of 2054´s with that cam/rocker set up and Tims Stage 2 heads, 45 Dells. They produce 149-151 hp and 210 NM torque max.
T

[qubek]

Thanks for your replies, I appreciate your input.

Hello.
Question is, do you want to take it apart and swop the crank ?

No

That combo can easily be tweaked (still on 69 stroke) and get up in the 135 hp range. But for a street car I would never do it on a stock crank. Not even a well balanced one. When reved high for longer periods of time, as on the freeway, the case WILL get pounded and have a short life. Racing bursts is a different game.

I try not to drive fast on freeway, except for short sprints. This of course means that I am moving rather slow, especially with stock, short gearbox I have, but I was always taught not to drive fast for too long with a type 1 engine. If I understand correctly what you mean, I'm already capable of attaining speeds that would be fatal for the engine if maintained for a longer period.

That said, you can increase the CR to 9,6 and get the heads reworked to something that matches a 1914. Going "Panchito" style wouldnt be bad.

This is what I was thinking about, although I considered even higher compression ratio. If my calculations are correct (and they don't have to be) and if the data on my camshaft taken from internet are correct (I've never measured it myself. I will probably have to) than looking at dynamic compression ratio, to obtain a figure around 8 I would have to bump the static compression ratio to over 10:1. Of course I know that DCR is just an abstract concept and we're living in the real word. "Common internet wisdom" tels me to keep this figure low. This is why I'm curious what ware your calculations/experiences. Sorry for asking, but I'm trying too check if my thinking is correct.

Especially when the header is on the large side, I have had very good luck with reducing lift on the exhaust a tad with that cam. Over time I have found some stock style 1,25 rockers that actually lifted 1,3. I use these on the intake and stay with the 1,25´s on the exhaust. That REALLY helps the engine to bleed torque. Usually I get round 100 NM/ liter and at a nice and wide band.

Sounds interesting, but I don't have stock style 1.25 rockers. What I can do is to use scat's 1.25:1 on the intake and stock 1.1:1 on the exhaust, but it's not the same. Plus I don't know if the difference wouldn't be too big that way. And wouldn't it cause problems with valve geometry adjustment?

Last year I built a couple of 2054´s with that cam/rocker set up and Tims Stage 2 heads, 45 Dells. They produce 149-151 hp and 210 NM torque max.

Nice. If you look at the comparison I have pasted above, my friend's engine is more powerful, but the max torque figure is similar. In your example torque is also much higher compared to mine, not only hp. And the difference in displacement is small.

Why do the torque and hp lines cross at 4800 something? and not 5252?

Maybe this is something I should have noticed myself, sorry, but I don't understand what you mean.


Zach, I didn't consider my venturis small actually. One more thing to think about

[Torben Alstrup]

The venturies are not the limiting factor on this side of 135 hp.
I use to say that a stock cranked, even well balanced, type 1 engine shouldnt cruise higher than 4500 rpm.
I also use to limit them at 5800-6000 rpm. and recommend customers to stay below 5000 in everyday driving, and use the last 1000 rpm to "when you need it"

When that is upheld the engines lives for a long time.
T

[Airspeed]

I am surprised Torben didn't notice this, but I see a very easy way to gain some hp and run your engine safer:
Your AFR is on the dangerously lean side!! running close to 14 AFR is not healthy (high EGT) and looses hp.
Have it tuned to 12.5-12.8 and your engine will thank you for it 

That is if the lower graph (of the first set posted) is not MAP in bar but really does show AFR...

[Torben Alstrup]

I thought it was MAP (?)
Apart from that, I agree.
T

[qubek]

It is AFR, but the reading is rather incorrect. There ware problems with attaching the probe to the exhaust. I suspect this may have been the reason.

As for the "safe" RPM's I generally fallow Torben's guidelines. Overly optimistic Autometer tacho helps

[Zach Gomulka]

The venturies are not the limiting factor on this side of 135 hp.

You know better than I, but I was thinking it's a little on the small side for the 40mm intake valves... once properly ported, of course.

[jaqo]

AFR reading is not accurate, don't look at it.

[Torben Alstrup]

Zach, you have to remember one thing. That is that Dells flow better than most carbs. If one wanted absolutely most possible top end, a larger set of carbs could and would be in its place. But for a street car, 40 mm Dells are quite alright for quite a lot of power. In that case on have to look at the power range along with driveablity.
On this engine, even 36 Dells would have done the job with only 1 or 2 hp loss at the top end.

Another thing is, that in this case the carbs are not the limiting factor. But if the heads were a set of top notch for the engine, and the cam was even 1 step up again, they would be very close to be maxed out. - Slightly modified 40 Dells pulls up to just around 150 hp. if the package is right. 140 hp is a walk in the park.

That´s why I wrote what I did. 
T

[Fiatdude]

What Torben said --- If you go to Higher Compression you will need to change cams, that cam does not work well with high comp.

If you want more performance without touching you engine ---- put a turbo on it --- the performance gains are fantastic and you DO NOT lose any of your drivability for street use -- and with a twist of a knob and 20-25# boost you can have 275-300 HP and that can be quite exciting
<
<
<   And this was done with the parts from AJ (LowBugget.com) (500 cfm 2 barrell and a T3-T4 turbo) and it is not a very expensive setup
<
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[qubek]

-> Fiatdude, I don't say that your advise is not good, but turbo is (for now) out of the question for various reasons.

-> Torben - what to you think about mixing 1.25 with 1.1 rockers? Or - if you think this may be not a good idea - could help me to get those stock style 1.25-1.3 ones you have been talking about? Do you have some for sale or do you know ware to find them? Where ware they used originally, wasserboxer?

[Torben Alstrup]

I found those 1,3 stock style while measuring a bunch of older SCAT rockers. Picked them out and used them where I found the need. I may have a few left.

BUT, - we have been a little around this one. My gutt feeling is to leave it as is, if you want a little life out of it. Adding 1,25 rocker s will aid a little in performance. But it will also "encourage" you to rev it higher. Your combo is not exactly high rpm proof. So, as I wrote earlier, if gains were to be found, you should first swop the crank and get the rotating assembly balanced.

T

[Zach Gomulka]

Thanks for the info Torben, I always look forward to what you have to say
A bit off topic but, how is it that Dells flow so much more than a Weber of the same size?

[Torben Alstrup]

That will be a layman´s answer, as I have no scientific info on that.
It most likely is the way that the secondary venturies are shaped different.
I have also noticed that IDF´s are more sensetive to stacks and the height of the stacks than DRLA´s. If we look at optimum intake runner length in a specific set up, at least the 40 & 44 IDF´s almost always "like" to be on the longer side of the calcutated length. That suggests that it has something to do with the secondary venturi.
The 40 IDF 68/69 are the best and can make good power. The 70/71 is hard to even pull 130 hp out of. But the 70/71´s are also very narrow at the intake. They almost cry out out for some machining before use.
T

[qubek]

The problem is that I feel a little bit like that:


On the one hand, there is my girlfriend saying that if I start to “improve” the engine now, I will not make it work again before July and we will end up going to Bug In in her Beetle again. Knowing me (not as well as she does, but well enough ) it is likely. Myself, I also like the saying “If it ain't broke, don't fix it”. It’s asking for trouble. And this is a very nice engine, in an everyday use. Actually I’m less concerned with the high RPM issue. I am more afraid of screwing something up, or doing a lot of work and attaining little gains in the end.
On the other hand, I have my little brother saying that this engine could be better. And I have this little wish to get into fourteens. But this would be difficult even with all the changes discussed above (except for the turbo, of course).

The choice is either to improve this engine without dissembling the bottom end, or to leave it as is and start to build a second one... which seems to be a better way, but will take a lot of time.

Of course I don't ask you to make the decision for me, but this discussion was/is helpful, so thanks.

[Torben Alstrup]

I love the Donald picture 

I vote for leaving it alone and start building another one.

T

[Harry/FDK]

The choice is either to improve this engine without dissembling the bottom end, or to leave it as is and start to build a second one... which seems to be a better way, but will take a lot of time.

 

[jaqo]

little brother? pfff
Since he has to take the engine out anyway, a little bit of port & polish would not be a bad idea, I think.
Torben - everything is balanced in this engine. Of course - it's still a stock crank

[Frallan]

Kubo, you know this si not my kind of topic as I have littel or no experience on thsi type of engines.
BUT what I have a lot of experience on and I mean a LOT, is driving and building at the same time. Many configuratiosn ahve gone through my eager fingers in modifying.
Always or almost always with low mileage in return.
I love it but at teh same time I wish I had the had one basic engine that ran with less power.

You came to the best conclusion ever yourself, keep this as it is with minor changes and enjoy it.
Start projecting a long term powerful engine and let it take a year, two or even more, as long as the finances are keeping up with your ambitions.

[Udo]

I think he needs some better heads or porting of his heads...

Udo