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What is the best cam profile for turbo application?!?!?

Posted: Dec 17, 2021 11:16 PM
by 5timesturbo
Like the title states....I’m going to my stage 3 setup and I’m thinking about including a cam. I’ll be running mega squirt, intercooler and I’m not sure what size injectors yet. I would like to get a nice daily/track driving 600hp. Maybe not be at 600 everyday but track days can be long. Anyway any suggestions is appreciated.

Re: What is the best cam profile for turbo application?!?!?

Posted: Dec 23, 2021 5:54 PM
by Preyupy
Most of the testing I have seen done over the years show that there isn't much difference between a N/A cam and a "boosted" cam. What makes a cam better and/or worse N/A does just about the same thing boosted. More lift and duration moves more air under all circumstances, big thing you will notice is the loss of a smooth idle when you start getting a lot of overlap. The really big cams are usually designed to make their power in the high RPM range (6000-8000 rpm) with an appreciable loss of low/midrange torque. Most Turbo engines don't rely on high RPM to make their power (a turbocharger that can efficiently flow enough air for an 8000 rpm engine usually is so large that the LAG at the lower rpm makes it very hard to drive). Also the high overlap cams are not as fuel efficient as they tend to allow more unburned air/fuel to pass right through the combustion chamber when both valves are open.

I would choose a mild or mid range cam for a Turbo application. Make sure you check your valve springs! The intake springs need to withstand the extra load of your boost pressure (a 46mm intake valve is roughly 2.5 sq/in so 10 psi of boost is exerting roughly 25lbs of force trying to open the valve for instance).

Re: What is the best cam profile for turbo application?!?!?

Posted: Jan 03, 2022 3:13 PM
by Rust Bucket
I had a quick look at your other thread.I assume you have a forged bottom,stock head,stock intake manifold.Not sure about the turbo manifold.

I have a thread on Speed-Talk(a place where engine builders discuss)about turbocharging the M30 and camshaft came on topic,of course.
I have all the OEM M30 camshaft at my disposal and intent to send one to the regrinder.There is no doubt the B35 camshaft is the best for
turbo application simply because it got the biggest lobe separation angle,meaning very little,none or even negative overlap.And plenty lobes
left for your desired profile.

Boost can further the torque curve higher in the RPM,to a point.The M30 is a formidable torque machine,and does spool a turbo rather quickly.
A more agressive camshaft would bleed off that precious low RPM action and the head,in stock trim(you got B34 right?) cannot take advantage of
hi RPM action anyway.

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A guy on Speed-Talk been nice enough to compute something ressembling my M30(3400cc quenched hemi inline six with pitiful flow numbers and
a very restrictive turbo log(using 745i stuff),on a engine simulation software.This in turn gave us a desirable camshaft profile.Intent of this cam
is not to turn the M30 into a screamer.It's intent is to allow the M30 to deal with a generous quantity of boost.Which from the little I know about
your build is what you should aim at.

Here's the link to the thread: https://www.speed-talk.com/forum/viewto ... 15&t=63857

Been a while I looked at it but from what I remember,you want the B35 cam,advance it(adjustable cam sprocket) and have the intake opening
lobe ground if needed,depending how much you advanced the cam.Take it for what it's worth,this is rough data.Everybody more than welcomed
to discuss this.

I have two build on the shelves,one is my M106 I intent to make a responsive engine(fast spool)for a manual car.Second build I have three M102
waiting to be destroyed for science.These will be heavily ported,port floors will be epoxied and reshaped,zero fack given under 3500RPM.
It will use a automatic transmission(2004r) with a stall and a 50hp nitrous shot if needed.

The first engine use M30 attributes,low RPM torquey engine with good mixture motion.Stockish head,intake manifold,not so much porting.
The second engine(s),does not use M30 original attributes,will need intense porting,custome intake manifold,lots and lots of research and
you are pretty much on your facking own,this is no 2JZ with tons of knowledge and support,when wanting to push the enveloppe.

I'm getting off bat here but there it goes.From what I know about your build,that is forged bottom and stock heads.If you wanna go the
next step,you need the latest,baddest turbo.I guess you have ARP headstuds and a good gasket,oringed block or head.Get that B35 cam and
have it ground a couple degrees on intake opening and advance the cam a couple degrees,dunno how much.Have a good valve job done,
might want a little bowl job done,do not enlarge intake ports.Exhaust valve are suceptible to burn and crack,might want to upgrade.

Re: What is the best cam profile for turbo application?!?!?

Posted: Jan 13, 2022 3:27 AM
by 5timesturbo
Sorry for the delay in reply...I was checking the thread for about two weeks and got no response...so I gave up. Thanks for the advice!! As for the hat I’ve got planned so far: 8.5:1 turbo pistons, TCD manifold, forgot the turbo, and ofcourse mega squirt. I’ve talked to Ireland engineering and they’ve got a 270 cam that seems mild enough to work.... How does that compare to the b35 cam?? I’m possibly willing to go the cam adjustment route...I’d just need more info and someone to walk me through what needs to be down to get the results I’m looking for. Valve springs, valve guides...ARP everything is a no brainer if you want to do it right from the start. Any other suggestions I appreciate it. It’s winter....engine building time. Lol