ZROSSA Posted August 18, 2008 Share Posted August 18, 2008 Howdy all. This is not z related but engine size is similar so hopefully someone can hekp out. I bought a 79 bmw 635csi about 6 weeks ago. Its a cool car but need MORE POWER! Thinking about a low boost turbo set up run by megasquirt. The engine is a euro spec M90 3.5L with a compression ratio of 9.3 to 1. I will run an intercooler and 95 octane fuel. I think I can get away with about 11 psi of boost. I would like boost to kick in aroun 2500 rpm if possable and make good power to 6500 rpm. I dont want to over heat the air at higher rpm so would give away a bit of low boost for better top end efficiency. Would this turbo do the trick? http://www.trademe.co.nz/Browse/Listing.aspx?id=170871867 I like the price. Forgot to add I would like about 350hp at crank. Cheers, Douglas Quote Link to comment Share on other sites More sharing options...
JSM Posted August 18, 2008 Share Posted August 18, 2008 I would pass on that one. It looks like one of the cheap chinese model turbos. I also think it is to small for your application. Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 18, 2008 Share Posted August 18, 2008 Howdy all. This is not z related but engine size is similar so hopefully someone can hekp out. I bought a 79 bmw 635csi about 6 weeks ago. Its a cool car but need MORE POWER! Thinking about a low boost turbo set up run by megasquirt. The engine is a euro spec M90 3.5L with a compression ratio of 9.3 to 1. I will run an intercooler and 95 octane fuel. I think I can get away with about 11 psi of boost. I would like boost to kick in aroun 2500 rpm if possable and make good power to 6500 rpm. I dont want to over heat the air at higher rpm so would give away a bit of low boost for better top end efficiency. Would this turbo do the trick? http://www.trademe.co.nz/Browse/Listing.aspx?id=170871867 I like the price. Forgot to add I would like about 350hp at crank. Cheers, Douglas compression is too high to run 11 psi. think about running 5 or 6 psi max. A power band from 2500 to 6500 is going to be tough to get. 3500 to 6500 is more like it. that turbo you are looking at is too small. You need around a T04B-62-1 trim compressor or a T04B-H3 for a low boost, 6500 rpm 3.5 liter. The turbine selection is also very important. I would call a few turbo shops and get some recommendations. I would guess a T4 turbine would be required for a 3.5 liter or maybe a very opened up T3. What is the hp of a 3.5 liter 635? if it is making 200hp and 225ftlbs of torque with no boost then it should make 280hp and 315ftlb 0f torque with 6 psi of boost. Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted August 18, 2008 Author Share Posted August 18, 2008 Thanks guys, I thoght it was a bit small. I really need to keep this as cheep as possable. The zed is eating money right now so just keeping my eye out for deals. The stock hp is 218 and tourque 228lb. Neat car, Has a close ratio dog leg 5 speed and lsd all standard. I will run a inteercooler. Thought I would be able to run more then 6psi. Will go back and read maximum boost .....again. Cheers, Douglas P.s. If any one comes across a good turbo for cheep, pls let me know. Shipping shouldnt be to big a deal or maybe we could send to my Dad in Atlanta. Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted August 18, 2008 Author Share Posted August 18, 2008 This looks like a better one http://www.trademe.co.nz/Browse/Listing.aspx?id=171662986 Guess im am better off spending a few more buck now........then later replacing junk Douglas Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted August 18, 2008 Share Posted August 18, 2008 Pyro is right - go for a 3500-6500 range for boost. A Garrett 60-1 w/ stage 5 .82 A/R Turbine would work or a GT35/40 w/.82 A/R turbine would be ideal. Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 18, 2008 Share Posted August 18, 2008 I used this site to find a good compressor match. http://www.squirrelpf.com/turbocalc/ the T04B 60-1, or 62-1, or even a H-3 works ok. didn't check the gt35/40. I used 305hp, 3.5 liter, 12.5 a/f, 0.47 bsfc, 1.5 psi IC loss, 6500 redline, 6000 max power, 3500 max boost, 3000 min boost. 6.5 psi to make 305hp. Yes, a free flowing turbine is important especially with a non turbo cam. A stage 5 0.82 a/r is a good choice. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 20, 2008 Share Posted August 20, 2008 9.3:1 isn't too much for 11 psi. The mitsubishi evo is 9.0:1 and runs 21 psi from the factory on american premium. He has new zealand 95 octane. A LOT of it depends on your specific engine and how well the combustion chamber is designed. You may need to find some beemer forums where they are familiar with that motor to help you out on that one. They're right, though, 2500~6500 is tricky to attain; maybe if you drop 1krpm off the bottom end of the band. If the heads flow worth anything you won't need 11 pounds to get 350 at the crank, however. EDIT: Pay close attention to the turbo you linked. It's a chinese unit. Use images on ebay listings to help you differentiate from genuine turbos (usually the compressor housing has letters/numbers cast into them on real ones) and absolutely avoid the chinese turbos like the plague. How cheap will it be when it grenades and drops little bits of metal into your intake manifold and oil pan? Quote Link to comment Share on other sites More sharing options...
texis30O Posted August 20, 2008 Share Posted August 20, 2008 parents had a 635 back in the late 80's. I used to drive the piss out of the thing. It would blow head gaskets all of the time, without redlining.....you might want to re think boosting that car......don't get me wrong I love dit but it just would not hold up to abuse at all........ Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 21, 2008 Share Posted August 21, 2008 Yes, that is right, cr and boost depends on engine design. But knowing that BMW made that NA engine with only 9.3:1 cr, I would assume adding 11 psi to it would be way too much. FYI, USA rates fuel octane differently. Our 93 octane is equal to 98 over seas. Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted August 21, 2008 Author Share Posted August 21, 2008 Just re read maximum boost last night. Looks like i can get away with 11 psi with good intercooling. Might have to do a water intercooling set up becuase of space and I think that will help a bit. Looking at a holset turbo at the moment. Garrets here are close to $2k. Bit rich for something that needs to be hidden from the wife. I am not in hurry so will just keep my eye out for a turbo thats suitable. Maybe get the mega squirt up and running first. Thanks for the input. Douglas Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 27, 2008 Share Posted August 27, 2008 Be careful. I know BMW has a bit of an engineering arrogance problem. For example, if it takes x thickness for something to hold without failing, they will use 1.05x instead of 1.6x like most cars are built. Some of their engines are rather like glass if you mess with them much. Sure, they can really engineer an engine for performance, but not all of them put up with "tinkering". Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.