Compression ratio

With Turbo and Super charging you can create massive horsepower with vw motors.

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markysparky1973
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Compression ratio

Post by markysparky1973 » Sun Sep 03, 2017 4:13 pm

Hi new to this site building a motor for my camper it's 1776 with efi going to be running a garette T3 what compression ration would you guys run at ????

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Chip Birks
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Re: Compression ratio

Post by Chip Birks » Sun Sep 03, 2017 10:40 pm

What fuel, how much boost?

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petew
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Re: Compression ratio

Post by petew » Mon Sep 04, 2017 12:03 am

You also better tell us what trans/R&P you're using and what you use the camper for. Short picnics or long holidays? How heavy is it?

markysparky1973
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Re: Compression ratio

Post by markysparky1973 » Wed Sep 06, 2017 3:48 pm

Hi it's running on unleaded it needs to be reliable for sort and long trips it's on a standard trans at moment but that will change later ,the boost I will tweak to suit

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petew
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Re: Compression ratio

Post by petew » Wed Sep 06, 2017 11:55 pm

I'll be interested to hear what Chip has to say, but I'd suggest you don't want to go above 6 or 7psi of boost. I also think you'll need plenty of oil cooling capacity (unless you're in a cold climate). Stock comp ratio will probably be ok (8:1), but you'll really need to watch how hot everything gets. It will be better if you can use a proper intercooler, probably water to air.

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Chip Birks
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Re: Compression ratio

Post by Chip Birks » Thu Sep 07, 2017 12:37 am

I'd suggest building a thick wall 1835 for a bus. Keep compression mild. 8:1 is probably not a bad idea. Keep boost nice and low as well. Not building a race car. If you can fit an air to water intercooler, I'd highly recommend it. Especially with an old turbo like the t3. Temps will be your enemy and that intercooler will keep them under control. While i like the idea of chemical intercooling, ie water/meth, it does require regular checking of a consumable, and if tuned for it your engine will go pop if you run out. Some folks have had really good luck with it, clonebug is one, he runs a ton of boost through his ity bity turbo and makes great, useable power. I don't think you are going to need 20+ psi to enjoy the added power a turbo will provide. An intercooler will make for a very "set it and forget it" setup.

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petew
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Re: Compression ratio

Post by petew » Thu Sep 07, 2017 6:25 am

I like Chip's idea of going thickwall 1835. The bigger the motor, the quicker it will build boost and be more linear to drive. You wouldn't want to go less than 8:1 comp ratio or you'll end up with quite a laggy engine.

Re water to air setups, you have LOTS of room under a camper for intercooler radiators (and oil coolers). The parts are pretty cheap anyway.

markysparky1973
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Re: Compression ratio

Post by markysparky1973 » Tue Sep 12, 2017 4:23 pm

Hi thanks for all the advice got a large oil cooler remote fitted to van already was thinking of running less than 10 psi and gona fit a intercooler under van

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petew
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Re: Compression ratio

Post by petew » Tue Sep 12, 2017 5:12 pm

Just out of interest, what part of the US do you live in?

On a related note... I went looking on the web but couldn't find this... The Race Shop twin cab bus towed the Inch Pincher/large car trailer backward and forward across the country with (for the time) a large stroker motor with IDAs IIRC. Lots of people at the time couldn't figure out how the engine lasted. Apparently the solution was a helicopter oil cooler with a thermostat. With this setup the engine dealt with a lot more load and heat than anyone would have expected. When the bus was found a few years back, it still had it's original motor in it. I think Richie Russell owns it now. Which just goes to show it's all about dealing with the heat. :)

markysparky1973
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Re: Compression ratio

Post by markysparky1973 » Thu Sep 14, 2017 5:31 pm

Hi im in the UK yeovil in Somerset so a nice cold climate to run a turbo bus in lol

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petew
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Re: Compression ratio

Post by petew » Thu Sep 14, 2017 6:53 pm

Yeah, that's a prime location for boost. You could run it with 6psi first. Watch your head and intake temps. If they're not too high on long freeway runs, up it to 10psi, then higher still if it's happy. :)

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seabeebuggy
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Re: Compression ratio

Post by seabeebuggy » Mon Sep 18, 2017 11:27 pm

Ive had 8.3:1 and now 7.8:1 major difference. I can run 20 lbs on 94 octane. Before I was 100 octane and pinging. It's a combo of many things. Do you want low grunt power? higher CR. do you want higher boost lower CR or you do both high cr and higher boost but you will need to do many things to prevent Detonation. Good fuel, boost adjusting timing. EFI better than carb. Inter-cooler. More oil help some but it needs to be 7 or greater Qts. add an additional oil cooler with fan. Any slight out of tune and say goodbye to the pistons and or rings. Been there and done that.

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