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Sun Mar 05, 2006 8:30 am

As some of you know Im in the process rebuilding my 2.1. I spoke to Boston Bob and he reccomends that I use the Brazilian Cofap pistons & Cyl. He says the lower compression is a good trade off for the couple of HP I'm going to lose (not that I have many to lose!). I am leaning towards sourcing out a german set. I have read that the brazilians have fuel burning issues due to the different shap of the piston head surface. The cofap are a couple of hundred $ less, but I would rayher spend the money and do it right.
Im not interested in puttting any chinese sets and the gowesty set I would have to use my cyl which one is toast. That along with they want $1k for the set and I think that is excessive. Im looking for options on which to go with.

Sun Mar 05, 2006 7:23 pm

It is truly sad that the Wasserboxer world does not have all the engine upgrade parts available to the Type 1 A/C platform. (Gene Berg Enterprises, Bug Pack, CB Performance, SCAT, ect., ect...)

For OE German P/C's try: http://www.bus-boys.com/parts1.9.html#pistons

Perhaps more power can be had with some head work. Boston Bob does offer the "Stage III: Big Valve Upgrade" Option on their 2.1 rebuilds:
http://www.bostonengine.com/enginepricelist.html#waterlngblk

In the Air Cooled world, big valves also require a larger diameter exhaust system, or you'll run hot. Not sure about catalytic converter water cooled Vanagons.

I've been thinking about rebuilding the top of my 1984 1.9L. Compression is low ( but hey, its got 217,500 miles!). I'm still researching the P/C issue too. Its too bad that Go Westy! seems to be the only source of decent pistons http://www.gowesty.com/piston_story.htm

Thought I'd try either RIMCO ( http://www.rimcovw.com/ ), or Steve Hollingsworth ( http://66.225.214.60/vwpsteve/ ) for some head work, before sending Go Westy! $1000 for a new set.

Mon Mar 06, 2006 3:31 pm

I called go westy and they are not selling thier piston/cyl outright anymore. So that option is off the list.
I have been doing some research and the lowered compression may be a good thing. With the drop in compression so will the hp drop (about 4-6HP), but longevity of the engine will go up do to lower cyl head temps and lower detonation.
Boston Bob is really pushing the brazilian Cofap pistons and says he does not recommend the stock compression german set.
I think if a high mileage engine is more important than a few HP, the brazilian set with German rings may be the way to go.
Looking for some commentary. :D

Mon Mar 06, 2006 4:18 pm

I trust Boston Bob's opinion.

I would like to run down there and meet him sometime.

Although I would doubt he would want to run up here to meet me. :shock:

Mon Mar 06, 2006 6:14 pm

I would highly recommend not using the brazillian cofap P&C's. Because the pin heighth is 1mm higher, giving it over .080 in deck heighth. This will destroy the squish area and the burn of the fuel. What this will cause is poor fuel efficiency, low performance, and difficult FI tuning. What I am working on is piston sets from JE Pistons and boring of stock cyls (because the piston will be oversized). Otherwise, I would buy a new stock german set with pin heighth in the correct location, or try to find used P&C's that match up.

Dpazos, if you send me your old piston set, I will try to match some up with your set. Right at the moment, I have a few used P&C's. Give me a call or email vwpsteve@cs.com

Steve Hollingsworth
VW Performance Phoenix, AZ
(602)-442-8997

Mon Mar 06, 2006 6:45 pm

Steve, From my understanding the piston pin being higher on the piston reduces the compression ratio from 8.6;1 (OEM) to 8.3:1 (cofap). Wouldn't the FI compensate the air/fuel mixture via monitoring through the Oxy. sensor? I know I will lose a few HP but the lower c/r will couse less heat and strain on the heads. Am I wrong in my assumptions?
I dont want to match up what came out as they are the cheapo chinese 2178cc set with the ridiculously high compression (10+:1) and one is in three pieces. Thanks for the offer though!

Mon Mar 06, 2006 9:45 pm

dpazos wrote: Steve, From my understanding the piston pin being higher on the piston reduces the compression ratio from 8.6;1 (OEM) to 8.3:1 (cofap). Wouldn't the FI compensate the air/fuel mixture via monitoring through the Oxy. sensor? I know I will lose a few HP but the lower c/r will couse less heat and strain on the heads. Am I wrong in my assumptions?
I dont want to match up what came out as they are the cheapo chinese 2178cc set with the ridiculously high compression (10+:1) and one is in three pieces. Thanks for the offer though!

The higher pin heighth will lower the compression to 7.9 and like I said above the squish area will be ruined. These engine were designed to run only .040-.045 decks to work properly. And no the FI system will not compensate the change in cr. I have played and played with this, doesn't work. The FI works best with the tight deck and cr's from 8.6- about 9:1 The performance engines I am going to build will be no higher than 9:1. Most in the 8.6-8.8.

Steve

Tue Mar 07, 2006 6:46 am

Please show me your math calculations for the 7.9:1 or the calculator you used. Many discussions throughout the web state that the 1mm difference lowers the compression fron 8.64:1 to 8.38:1. using the following calculators I have come up with 8.3:1. I think 8.3 to 8.6 is somewhat acceptable, but 7.9 is not.

http://www.csgnetwork.com/compcalc.html
http://www.1800vw.bizhosting.com/compression_computer_2.htm
http://www.1800vw.bizhosting.com/motor.computer.htm

Tue Mar 07, 2006 8:43 am

Engine Specs
# of cylinders 4
bore (mm) 94
stroke (mm) 76
deck height (") 0.04
combustion chamber cc's 15
piston notch cc's 47

Displacement (cc) 2109.63
Displacement (ci) 128.73
Deck (cc) 7.05
Compression Ratio 8.64

Engine Specs
# of cylinders 4
bore (mm) 94
stroke (mm) 76
deck height (") 0.08
combustion chamber cc's 15
piston notch cc's 47

Displacement (cc) 2109.63
Displacement (ci) 128.73
Deck (cc) 14.10
Compression Ratio 7.93

Tue Mar 07, 2006 9:44 am

Quote: Engine Specs
# of cylinders 4
bore (mm) 94
stroke (mm) 76
deck height (") 0.04
combustion chamber cc's 15
piston notch cc's 47

Displacement (cc) 2109.63
Displacement (ci) 128.73
Deck (cc) 7.05
Compression Ratio 8.64

Engine Specs
# of cylinders 4
bore (mm) 94
stroke (mm) 76
deck height (") 0.08
combustion chamber cc's 15
piston notch cc's 43

Displacement (cc) 2109.63
Displacement (ci) 128.73
Deck (cc) 14.10
Compression Ratio 8.35

I found our discrepancy. The cofap piston dishing is slight different than the german set. it is actually 43cc not 47cc and that is what is throwing your calculations off. I inputed the numbers in bold above. the dishing slightly compensate for the increase deck height and bumps up the c/r.

I also did the calculations for the chinese set that have an even different dishing:

ngine Specs
# of cylinders 4
bore (mm) 95.5
stroke (mm) 76
deck height (") 0.08
combustion chamber cc's 15
piston notch cc's 48.5

Displacement (cc) 2177.57
Deck (cc) 7.29
Compression Ratio 8.69
I don't see how gowesty can say that these have a 10:1 compression ratio. they look spot on. They seem to slightly increase the displacement and keep the CR the same I am still skeptical about thier QC.

Tue Mar 07, 2006 10:02 am

EDIT! Ooops! I forgot to add in the deck height difference of 1mm on the chinese set. That brings the compression down to 7.97:1. Now I know why those chinese pistons had so much carbon within 10-15K. Are my calculations off or is gowesty completely wrong? I have double checked them and I dont think they are.
I definately would not use these, but not as bad as the high compression worries gowesty is claiming.