Looking For Advice on a Camshaft

[jc052685]

Hello, a few on here a familiar with my build but for those that are not here you go.

 

Stock L28et (lots of miles!)

p90 head

n42 intake

240sxtb

2.5" IC pipe

huge front mount

440cc injectors

msnsII

open exhaust

3" custom DP

turbonetics 62-1 stage-5 (http://www.turboneticsinc.com/products/index.php?products_id=901&category_id=89)

 

let me know what other info would be helpfull.

 

Here is a rough drawing of the dyno

 

 

 

I am trying to move the peak torque up. I would like my power to be made in the 3500-6500 maybe 7500 rpm range. I do not want to sacrifice any torque. I plan on calling schnieder cams this week also. I just think the people here would have a better idea what I need or at least could help me with what I should be able to ask the sales/tech person.

 

THANKS,

JEFF

[BRAAP]

The intake manifold itself is the biggest red flag I see, especially when looking at your torque curve.

 

Your torque curve is indicative of typical OE L-6 EFI intakes. Keep in mind that the OE EFI intakes, ALL of them, have a runner cross sectional area that is only 53% the cross sectional area of a 280-Z intake valve! You can see the bottle neck here.

 

Now there are couple/few members that have been able to produce torque curves biased more towards the upper end of the RPM band with the OE EFI intake, but most if not all of those have some form of modification for enhanced flow, and those examples are the exception, not the rule.

Once you swap out to different intake, whether it be an SU intake modified for EFI, a custom scratch built intake, or even the 4bbl intake set up for EFI, with everything else you have, just retune the MS for optimum power, your torque curve will be much more robust above 3600 RPM which means your HP figure will be much higher, if not being a larger number than your torque figure!

 

Regarding cams. For Turbo L-6 engines, cams are still in the magical black art realm. With what little documented development regarding Turbonic L series cams, it seems everyone has an opinion on what lobe specs work, many have had a custom cam ground, and as far as I can tell, pretty much all of these have worked successfully for that particular application! Even David Vizard talks about a wild beyond belief cam profile with NO overlap that produced over 1000 HP on street driven SBC! We have members here that have made great power and run phenomenal ¼ mile times with the Z-gad grind. Garrett has ran low 11’s in his Turbo L-6 powered street 280-Z car with the stock Turbo cam and Thagard intake manifold! Another credible source prefers a particular stock N/A grind on performance Turbo L-6’s!

 

If it were an N/A, Supercharged, or Nitrous charged L-6, or even an SBC, I feel comfortable with coming up with cam specs for those application as the variables involved are pretty consistent and fairly well known. Make it a Turbo and with the continually changing intake to exhaust pressure ratios involved, the optimum intake and exhaust valve event timing now is going to be totally different, and depending on the always changing int-exh pressure ratios within the RPM range, throw in differing intake and exhaust Turbo housing designs, different turbine and intake impellor designs, just slightly changing the cam specs, lobe separation angle, etc, will alter the intake to exhaust pressure ratios again therefore requiring a different cam lobe profile for optimum performance. You can see how this becomes a viscous cycle, akin to a dog chasing his tail….

 

I will offer this tidbit of advice, first time mentioned publicly anywhere regarding Turbo L-6 camshafts. I keep in touch with Rebello Racing on a semi regular basis. In those talks with the owner, the discussion of L-series heads is always the core topic. Being as he has probably more L-6 dyno time than anyone in the country, I personally put a lot of faith in his opinion regarding what does and does not work on the L-6. Regardless of the absolute numbers his dyno declares, it is within those numbers of what combo produces more and most consistently that I’m interested in. In his playing and tinkering with the Turbo L-6’s on the Dyno, he has developed an affinity for one of the stock N/A L-6 cams. Which one? Well, "A" grind N/A cam. He prefers it over the stock Turbo grind and even the other aftermarket Turbo grinds he has tested. (we are currently building a very custom P-90 head for a Turbo application, with 1mm oversize Ferrea exhaust valves and one of these cams with Rebello springs, which will be up for sale, very soon…)

 

I short, I recommend you leave the cam alone and spend your money/time on an intake manifold. Then, if you are not satisfied, look at a different cam, possibly a stock N/A Cam...

 

Hope that helps,

Paul

Edited September 4, 2010 by BRAAP
Gave up cam desig.

[jc052685]

yes, I have a web site bookmarked with all the stock cam grinds and all the NA profiles had a greater amount of overlap. I know the 260z cam is suposed to be the "hot" cam. I have loads of L-6 pars laying around so I may tinker.

[Clifton]

I'm with Brapp on the manifold being the problem. Short, larger runners would do more for you than a cam. I've dynod with a stock efi mani, custom mani with stock cam and custom mani with a bigger cam, all turboed and both dynos with the custom mani held the torque and HP longer. I have my last one posted on here somewhere.

[jc052685]

how come several I have seen on here have done better than 300whp on a factory manifold? Someone else here in town put down right at 360hp/360tq with factory manifold and some mistery cam that he could not remember what or where it came from. I did so much searching last night after Braap's inital statment of the lack of intake manifold flow. That is when I saw several making over the 300hp mark on the stock mani. I dont doubt that it is restrictive I am just curious what my problem is??!?! I did notice today I was a bit lean at peak TQ (12.1:1) and I knew I was very rich up top (10:1). I know there is hp to be had up top and I plan on getting the tune alot closer in the up comming weeks. I just ddont see myself making the 300hp with a tune, but i dont know, maybe it will?

[Clifton]

I'm sure you can make 500 rwhp on a factory manifold. I'm saying that in my experience from the dyno, a larger, short runner will do alot more for your power band than a cam. A lot of making power is in the boost and turbo choice. You run enough boost and you will make the power. Most don't though.

[jc052685]

ok, that sounds fair enough......

 

I was just not looking to do the intake until I did the head at the same time. That way both could be paired together. I guess I will be looking into the Lonewolf manifold I have been drooling over for years, man the look good. Just hope they are worth the money, though I am sure they are!

[Clifton]

Runner length is a big determiner of the where peak torque is. I don't know if his runners are any shorter than stock. I'm sure they are larger though. I wasn't trying to talk you out of the cam. Just didn't want you to think the torque curve is all in the cam.

[2eighTZ4me]

While I haven't measured explicitly, I am almost sure the Lonewolf runners are longer than stock. I'll have to put the two side by side and get out the tape measure to verify, but from a cursory glance, the Lonewolf seems to be longer (and definitely bigger!)

[Bernardd]

I have a robello cyl head with these cam specs: 21BTDC closes 65 ATDC. Exhaust opens 65 ABDC closes 21 degrees ATDC lobe centers 112 overlap 48 duration 266. The moved the stock cam's torque curve up 200 rpm. The closest stock cam would be the L26 cam.

[Pyro]

Yes, a tune will increase torque by a lot.

 

10:1 is very rich. try to get 12.7:1 at full throttle

 

what does the ignition timing curve look like??

 

at what rpm does the turbo get full boost?

 

a stage 5 turbine should be delaying boost and hurting low rpm torque. Only use a free flowing turbine (like a stage 5) with a bigger cam (more overlap).

 

I use a stage 1 schnieder turbo cam and my engine pulls hard from 3000 to 6500. However, bigger cams have less low rpm torque. But, you can use more compression ratio with a bigger cam.

[jc052685]

I am peaking torqu at 3800 and 17 psi by 3600rpm. I am looking for this motor to make power from 3500 to 7000 or 7500. Car is not hardly driven on the street much. I spend most of the time n the upper rpm range. I am also realy wanting to keep the hp and tq close to each other. Like say 10%. I will post up my ign map later. not on this computer.

[z-ya]

A plot of AFR along with HP and torque would give us a lot more insight. What you really need to do is flatten the torque curve. HP is a function of torque and RPM, so the more torque at higher RPMs, the more HP.

 

The N42 manifold is good for well over 300WHP in a turbocharged application, so it is not the intake. It is either a bad tune, or the turbine is not flowing enough (I would think your turbo would not have that problem). I am guessing that your tune is way off. Spending an hour or two on a dyno should get you power in the 300WHP range with the stock camshaft.

 

T04B compressor/Stock T3 turbine, look familiar?

 

T04E compressor/Stage 3 turbine. Ignore the spool up time as after porting the internal waste gate I was able to get the same torque curve during spool up as above.

[Pyro]

It seems the stage 3 turbine killed the low speed torque due to lack of boost at lower rpms (3000).

 

A stock turbine works well with a stock cam.

A modified turbine (stage 3 to 5) works well with a longer duration cam.

 

What to4b compressor is that (s, v1/v2, h)?

[z-ya]

As per my post, the slow spool up time was due to the internal waste gate port being too small. Once I opened up the waste gate port, it hits full boost just like the stock turbine around 3000RPM. It was a T04B .60 AR compressor.

 

Pete

[Bernardd]

I have a robello cyl head with these cam specs: 21BTDC closes 65 ATDC. Exhaust opens 65 ABDC closes 21 degrees ATDC lobe centers 112 overlap 48 duration 266. The moved the stock cam's torque curve up 200 rpm. The closest stock cam would be the L26 cam.

 

 

Forgot to add that the lift is .490 on my cam.

[Tony D]

Let's put some numbers up on what a stock manifold sacrifices in the way of flow, shall we?

 

JeffP had 2XXCFM through the intake port, when matched with a 44mm Cannon Manifold suitably ported by B.C. Gerolamy.

This same port, when mated to a stock manifold which had been Extrude-Honed to a mirror finish and had a slight 'anti-reversionary' lip (manifold smaller than port in the head) flowed 30CFM less.

 

This was at 25" Hg.

 

Imagine what that number is when under pressure. Vacuum pressure drop over an orifice is one thing, the pressure drop over that same orifice can be an astounding number. What it translates to is much more flow at much less observed pressure on the boost gauge in the plenum.

 

8psi at, say 220CFM is a LOT different Pounds Per Hour number than 8psi at say 180CFM.

 

And the pounds per hour is what ultimately will determine what horsepower you will achieve.

[Pyro]

As per my post, the slow spool up time was due to the internal waste gate port being too small. Once I opened up the waste gate port, it hits full boost just like the stock turbine around 3000RPM. It was a T04B .60 AR compressor.

 

Pete

 

The wastegate should be more or less closed until full boost, so I don't understand how too small of a wastgate port would delay boost. ????

 

I can see getting boost creep from too small of a wastegate but not a slow spool.

[z-ya]

The wastegate should be more or less closed until full boost, so I don't understand how too small of a wastgate port would delay boost. ????

 

I can see getting boost creep from too small of a wastegate but not a slow spool.

 

Your right, I had an over boost problem with too small a waste gate port. Then I removed the boost controller which was set for 14psi. So you can see that the torque flattens out at 3600RPM, and then continues to climb. At 3600RPM the boost pressure was around 7psi, so the waste gate opened then, and the boost continued to creep to around 14psi (where I let off the throttle). After porting the waste gate I put the boost controller back in, and now it hits 14psi around 3200RPM, and stays there.

 

Sorry for the confusion.

 

Pete

[Pyro]

I see. good explanation!