M42 turbo fact thread

[wazzu70]

Whether or not you should think about replacing the rods depends on the amount of torque you intend to make. Around 350wtq is when I would really start thinking.

[MF DOOM]

wow I guess I sparked a lot of conversation lol. Which is awesome for me! thanks for all the input! So from what I've been reading custom grind cams are probably the best thing to do but since I'm super in experienced with turbocharging a motor and understanding how the cams should be ground I'm probably just going to go with the VAC turbo grind cams for no and maybe later in life when I know more about it I'll go for the custom ones lol.

So from what you all said the arrow rods are basically pointless for me to buy? I know the M42 internals are all forged and super strong but I figured I'll already be neck deep might as well get new rods since the rest of the motor is going to be basically new as well! I'm still up in the air about it so I don't know what I'm going to be doing as far as rods go =/ ....Honestly I still need to finish tearing my motor down and get it to the machine shop hopefully by the end of this month or early next month. That was over my winter break I can focus on getting that together :nice:

The more I get into this the more and more excited I'm getting about it!!! I also believe I'm most likely going with a garrett gt28rs or a gt2871r for my turbo because that's what my friends 240 with his sr20det has and it responds extremely well!

Thank you all again for the help and much needed input! Happy to know the boosted M42 community is a bunch of good people who pretty knowledgeable!

http://www.full-race.com/articles/bo...fr-turbos.html :up:

[pantelones]

A lot of the turbo cam info out there is from the early 80s when turbos were more exhaust restrictions than power adders. The old stock cams are best for boost assums you have a log manifold and a restrictive turbo with tons of backpressure.

Some turbo cam info on BF.c http://forums.bimmerforums.com/forum...ht=Turbo%20cam

Basically the moral of the story in the last article I posted.

And good links/thread you started! QFT...

There are basics to follow which are addressed in much of the reading material out there however it is up to the end user/builder to refine, thats where the experience comes in.

Basically my dilemma at the moment... I don't have the funds to start playing around and actually working with engine builders yet. In time, in time.

I called and asked for specs and the guy told me about them and said theyd be good for about 14psi and then we chatted about custom grinds. I was talking to Jim at MM during the time about cams, lifters and about a full head. The deeper I get into school the more I think Im going to have to wait on cams.. Itll probably be 4+ years before I do anything else to the engine but when i do ill probably go with a full MM head. For now its tune and drive.

Ahh I see, yeah this stuff isn't cheap... Again, funds are really the only thing holding me back. A manifold and intake would be a great project for me next year in my welding classes. ;D

wow I guess I sparked a lot of conversation lol. Which is awesome for me! thanks for all the input! So from what I've been reading custom grind cams are probably the best thing to do but since I'm super in experienced with turbocharging a motor and understanding how the cams should be ground I'm probably just going to go with the VAC turbo grind cams for no and maybe later in life when I know more about it I'll go for the custom ones lol.

Usually the company you work with can help you pick a cam, whether it be custom or cataloged. As stated before the VAC grind is much better than the stock cam, but it is not going to be perfect. There are fundamental differences between the N/A and turbo cam profile and just switching to that profile will help out a lot. Though, when you start upping the PSI and making a more efficient system, you can net greater gains, and reduce lag with a correctly designed cam for your specific set up. Personally though, I would go with a custom cam even for a low PSI set up as I would be the one making the manifold, and intake...

[ccsdo5]

wow I guess I sparked a lot of conversation lol. Which is awesome for me! thanks for all the input! So from what I've been reading custom grind cams are probably the best thing to do but since I'm super in experienced with turbocharging a motor and understanding how the cams should be ground I'm probably just going to go with the VAC turbo grind cams for no and maybe later in life when I know more about it I'll go for the custom ones lol.

So from what you all said the arrow rods are basically pointless for me to buy? I know the M42 internals are all forged and super strong but I figured I'll already be neck deep might as well get new rods since the rest of the motor is going to be basically new as well! I'm still up in the air about it so I don't know what I'm going to be doing as far as rods go =/ ....Honestly I still need to finish tearing my motor down and get it to the machine shop hopefully by the end of this month or early next month. That was over my winter break I can focus on getting that together :nice:

The more I get into this the more and more excited I'm getting about it!!! I also believe I'm most likely going with a garrett gt28rs or a gt2871r for my turbo because that's what my friends 240 with his sr20det has and it responds extremely well!

Thank you all again for the help and much needed input! Happy to know the boosted M42 community is a bunch of good people who pretty knowledgeable!

[MF DOOM]

I agree, but it seems like it's not quite as simple as choosing N/A cams. It's more or less making a cam for the motor as apposed to building a motor around a cam.

Also another really good article to read...

http://www.carcraft.com/techarticles/ctrp_1106_turbo_camshaft_guide/viewall.html

Does anyone have a cam card for the VAC turbo cams? Seems like that would be some good info for the tread since it's not stated on the site. Also MFDOOM when you contacted VAC were they suggesting custom cams or just giving you the option?

And if your wondering why I am bothering to post here, my next e30 IS going to be a turbo'ed m10 or m42... Was looking at buying buttchugz 84 318i awhile back, but slacked on it and it sold.

I called and asked for specs and the guy told me about them and said theyd be good for about 14psi and then we chatted about custom grinds. I was talking to Jim at MM during the time about cams, lifters and about a full head. The deeper I get into school the more I think Im going to have to wait on cams.. Itll probably be 4+ years before I do anything else to the engine but when i do ill probably go with a full MM head. For now its tune and drive.

[wazzu70]

Go to www.catcams.be and you can find the specs.

Choosing a cam for FI really isn't any different than atmo. Atmo cams also work great for FI if you have an efficient hotside. Turbo cams are usually just a hot intake lobe paired with a mild exhaust lobe and an advanced intake centerline to reduce overlap.

Obviously there are variations that could be better, but the gains are relatively minor compared to the jump from factory cams to a turbo specific grind.

A lot of the turbo cam info out there is from the early 80s when turbos were more exhaust restrictions than power adders. The old stock cams are best for boost assums you have a log manifold and a restrictive turbo with tons of backpressure.

Some turbo cam info on BF.c http://forums.bimmerforums.com/forum...ht=Turbo%20cam

[pantelones]

This is true of atmo cams. If you want it to be perfect it needs to be custom ground for your specific application. Even then, you can buy sport, rally, ect cams.

The VAC turbo grinds are a great all around grind that will work with most setups. Like all turbo cams you need a free flowing exhaust to really make them shine (no log mani, no rediculiously small turbine housing). The grinds aren't 100% perfect for all applications but its still leauges ahead of using stock garbage :)

I agree, but it seems like it's not quite as simple as choosing N/A cams. It's more or less making a cam for the motor as apposed to building a motor around a cam.

Also another really good article to read...

http://www.carcraft.com/techarticles/ctrp_1106_turbo_camshaft_guide/viewall.html

Does anyone have a cam card for the VAC turbo cams? Seems like that would be some good info for the tread since it's not stated on the site. Also MFDOOM when you contacted VAC were they suggesting custom cams or just giving you the option?

And if your wondering why I am bothering to post here, my next e30 IS going to be a turbo'ed m10 or m42... Was looking at buying buttchugz 84 318i awhile back, but slacked on it and it sold.

[wazzu70]

^^^ There is soooo much more that goes into a turbo cam than that!

Custom cams, custom cams, custom cams...

http://www.forcedinductions.com/help.htm

http://www.hotrod.com/pitstop/hrdp_1011_cams_for_turbocharged_engines/viewall.html

And for shits and giggles, put your calculus skills to work?


http://www.tildentechnologies.com/Cams/index.html

This is true of atmo cams. If you want it to be perfect it needs to be custom ground for your specific application. Even then, you can buy sport, rally, ect cams.

The VAC turbo grinds are a great all around grind that will work with most setups. Like all turbo cams you need a free flowing exhaust to really make them shine (no log mani, no rediculiously small turbine housing). The grinds aren't 100% perfect for all applications but its still leauges ahead of using stock garbage :)

[///digitalme]

Hi guys I'm new to this turbo thing. I'm getting to the point where I want my car to be. My engine is healthy. Full timing overhaul im thinking of getting it turbocharged. What's a realistic number of cost. My goal is atleast 160-190hp. Sorry about my noob questions lol also trying to keep cost low using stock internals.

[bmwm42]

What about attitude atmospheric pressure outside air temp density of fuel all this shit impacts your turbo build and should be considered when deciding your cam grind for your build

[pantelones]

You pretty much just described my engine. Cams would be worth it. I see a noticeable drop off after 6k and its almost not worth revving passed 6.5k. Talk to them about how much boost you plan to run. When I talked to them last they were getting a quote for me for some custom cams, they never got back to me btw, but depending on boost level and how high you want to rev they can set you up with more desirable cam specs than what is listed.

^^^ There is soooo much more that goes into a turbo cam than that!

Custom cams, custom cams, custom cams...

Back-pressure, RPM range, boost level, target horsepower, A/R of turbo, turbo frame (T3, T4, T6/Thumper), head flow, cubic inches, and even location of turbo...etc. All of these factors are extremely important in determining the cam that best suits your needs. There is no rule of thumb with a turbo cam. There are too many variables and the only way to get the right cam is to take all of those your parameters into consideration, and only then can a proper cam be selected.

http://www.forcedinductions.com/help.htm

In truth, Godbold says 99 percent of Comp Cams' turbo grinds should be custom profiles because "pressure differential can be all over the place. The reason we don't have a lot of catalog turbo cams is because there are not a lot of catalog turbo systems." Every turbo installation is unique.

http://www.hotrod.com/pitstop/hrdp_1...s/viewall.html


And for shits and giggles, put your calculus skills to work?

http://www.tildentechnologies.com/Cams/index.html

[gearheadE30]

Man, I've been perfectly happy driving my turbo M42 the way it is, and now you all have me wanting to start fiddling with it again and try to get more power...

[wazzu70]

The VAC cams will definitely spool faster and add more power than the wimpy OEM cams. Our factory cams are pretty weak sauce!

[MF DOOM]

And I have some low mileage ones i'll sell you :)

[Dj Buttchug]

fwiw ccsdo5, you dont really need to fork out extra money for rods. Stock m42 rods are insanely strong.