Camshaft grinds for turbo

turbo_bob · Post by **turbo_bob** » Thu Dec 28, 2006 9:02 pm

mschilling wrote:What do you guys think of having NO overlap? Good or bad for turbos?

I have 30 degrees overlap, are we talking MPG or ET. I run high 10's in the 1/4 mile with this amount of overlap.

Cam specs:
IO 18, EC 12, EO 62, IC 56
gross cam lift .343
1.5 R/R's at valve .513
running duration 295
duration at .050, 254
LSA 112
intake lobe C/L 109
exhaust lobe C/L 115
ground 3 degrees advance
30 degrees overlap

scott the viking · Post by **scott the viking** » Thu Dec 28, 2006 10:06 pm

I was referring to horsepower made on my dyno with different degrees of overlap. Like I said...zero works "in some circumstances".
30 degrees of overlap is really quite conservative. There are even a couple of stock turbo cars with that much. So your definitely not running a cam with too much overlap...as a matter of fact...I would say that is a totally reasonable number.
Just out of curiosity...have you ran a cam with around 8 or 10 degrees of overlap on this engine for a comparison?

turbo_bob · Post by **turbo_bob** » Thu Dec 28, 2006 10:23 pm

scott the viking wrote: 30 degrees of overlap is really quite conservative. So your definitely not running a cam with too much overlap...as a matter of fact...I would say that is a totally reasonable number.
Just out of curiosity...have you ran a cam with around 8 or 10 degrees of overlap on this engine for a comparison?

This V-26 cam is the ratio version of the W-120 cam, it is conservative by most here that run quicker than me.

The only other cam I tried turboed, and it is not an exact apples to apples comparsion with the manifold, throttle body, end castings, was the FK-7
IO 14, EC 6, EO 58, IC 50
gross cam lift .357
1.4 R/R's .500
running duration 288
duration at .050, 244
LSA 112
intake lobe C/L 108
exhaust lobe C/L 116
ground 4 degrees advance
20 degrees overlap

MarioVelotta · Post by **MarioVelotta** » Thu Dec 28, 2006 11:50 pm

Turbo_bob, what's the reason is for having your cam ground 3 or 4 degrees advanced?

turbo_bob · Post by **turbo_bob** » Fri Dec 29, 2006 2:59 pm

MarioVelotta wrote:Turbo_bob, what's the reason is for having your cam ground 3 or 4 degrees advanced?

Most all cams are ground at least 2 degrees advance.

ADVANCING
Begins Intake Event Sooner
Open Intake Valve Sooner
Builds More Low-End Torque
Decrease Piston-Intake Valve Clearance
Increase Piston-Exhaust Valve Clearance

RETARDING
Delays intake event Closes intake
Keeps Intake Valve Open Later
Builds More High-End Power
Increase Piston-Intake Valve Clearance
Decrease Piston-Exhaust Valve Clearance

http://www.webcamshafts.com/

MarioVelotta · Post by **MarioVelotta** » Fri Dec 29, 2006 8:59 pm

Nice, great info thanks.

70dragbug · Post by **70dragbug** » Wed Jan 03, 2007 4:24 am

This is a great thread

So far everything is clear to me.My questions are:
How does displacement fit into this picture,what are your experiences? I´ve noticed that larger displacement engines have more duration,more overlap and more lobe sepration than smaller engines in turbo applications. Why is that?

I´m building a 103x88 turbo type 4 - so would what would I be looking for in a cam? More duration,more overlap or more lobe seperation? It´s not really for drag racing use - more roadracing actually.So throttle response and overall power are important to me.

I realize that a certain amount of overlap is required to allow a good scavenging of the cylinder - even in a turbo application.Does this increase when increasing displacement?

Thanks,
Mark

mschilling · Post by **mschilling** » Wed Jan 03, 2007 6:52 pm

Correct me if I'm wrong, but it depends if you are using carbs or efi.

turbo_bob · Post by **turbo_bob** » Wed Jan 03, 2007 8:44 pm

70dragbug wrote:My questions are:
How does displacement fit into this picture

I´m building a 103x88 turbo type 4 - so would what would I be looking for in a cam? More duration,more overlap or more lobe seperation? It´s not really for drag racing use - more roadracing actually.So throttle response and overall power are important to me.

I realize that a certain amount of overlap is required to allow a good scavenging of the cylinder - even in a turbo application.Does this increase when increasing displacement?

The larger the engine, CI, the more one can get away with more duration. A 3.0 engine has alot more torque than a 1.6 engine, even if the RPM bands are the same.

I would shoot for .254 to .260 duration at .050, LSA 108 or less for NA, 108 or more for turbo.

No, your head design, port size, exhaust size, compression, CFM flow, will determine your cam duration. The cam duration along with the proper balance of head flow will determine the RPM band no matter what the CI's are.

70dragbug · Post by **70dragbug** » Thu Jan 04, 2007 2:21 am

No, your head design, port size, exhaust size, compression, CFM flow, will determine your cam duration. The cam duration along with the proper balance of head flow will determine the RPM band no matter what the CI's are.

That I do know as well - I just wanted to know if there was a link between cam duration,overlap and CI - Thanks Bob!

iswinkels · Post by **iswinkels** » Thu Jan 11, 2007 3:10 am

I've had 3 turbo engines so far. The first was a 1641cc with CB's 2242 294 intake duration cam with 1.25:1 rockers which made for 0.530" at the intake valve. Heads were stock CB 044's with dual springs. Made 165rwhp and the power was strong from 3700-6800 with a GT28-320 turbo and 16lb boost. 7.46:1 compression. 1 5/8" CB hideaway header. Intercooled and EFI with 380cc injectors and MSD ignition.

The second engine was a 2332 with a TCS10 cam and 1.25:1 rockers. Heads were 46x38 valved CB comp eliminators. 7.8:1 compression. Custom 1 1/2" header with a GT28-320 turbo and 12lb. Massive torque that peaked around 3500rpm. Ran out of power by 5500ish. 5.325" conrods and a short rod ratio are about the other factors. Also intercooled with EFI and 660cc injectors and MSD ignition. Never dyno'd due to discovering a lifer failure in progress (despite running 2000k's on single springs).

The new engine setup is a 2332 with a Web 86b 112LC with pauter 1.3:1 rockers. Heads are CB comp eliminators with 48x40 valves, CNC ported with Kmotion springs. Lift at the valve is just under 0.500" from memory. Custom 40mm ID exhaust header match ported to the heads with twin GT2554R turbo's running sequential bi-turbo configuration. 5.5" rods, 7.8:1 compression. Also intercooled with EFI and 660cc injectors, Distributorless 2 coil MSD waste spark ignition.

Hopes for the new combo are low 1st stage full boost by 2000 RPM, 2nd turbo by 4000-4500 rpm, and 25lb boost max with a redline around 7800-8000. I'd like to see 400-430rwhp. Turbo's are rated at 260hp each.

mschilling · Post by **mschilling** » Thu Jan 11, 2007 5:22 am

Sounds nice. What are the specs on the cam "Web 86b 112LC" and are you considering using staged injectors?

iswinkels · Post by **iswinkels** » Thu Jan 11, 2007 5:30 am

Actual Duration @.050" - 260, 0.383" at the lobe, and 112 degrees lobe seperation. Advertised Duration - 300 degrees. (from the aircooled.net website). 0.498" with 1.3:1 rockers which is my setup.

I've run up to 850cc injectors in sequential operation with pulse widths as low as 1.55ms without a cylinder dropping out because of bad fuel atomisation.

I'll be running the 660's for the moment, but if i have to upgrade i'll probably go straight to 850's or 1000's in the sard range. Some of sard low impedance injectors are stable to 1.1ms.

mschilling · Post by **mschilling** » Thu Jan 11, 2007 6:45 am

Qu' est que c'est "sard"? Is that a brand of inectors? Thanks for the cam specs, plenty of duration. Mine's going to have less but with the same 112LC. I just thought of the staged injector idea as it seems popular on the all out engines like yours. Even three stages are used like on the MPS Mazda where alcohol is injected to add octane when over 5k rpm, so there are plenty of options with separate injectors. Dual plugs are an option too (I think all these are available with your ecu).

bugsterkafer · Post by **bugsterkafer** » Thu Jan 11, 2007 9:32 am

Une marque de pièce