Hi guys,

after having a lot of headaches with my CETA, I finally put it on a DynoJet. It's a 2002 CETA coupe, manually shifted through a T56:

• LS1 stock bottom end
• stock LS6 MAF, Intake and TB
• MTI clear lid intake
• FAST 36# injectors
• AFR 205 heads w/ .660 BTR springs, Crane Gold Rockers etc.
• MS4 cam
• Hooker 1 3/4" Longtubes
• ORY
• Magnaflow exhaust

I scored 426rwhp and 387tq. I'm in Germany (yes, I already took it WAY past 150mph) so the numbers on the attached sheet are metric. I also attached an HPT log of the run for anyone who is interested. I'm still very conservative with spark and there are a few things to optimize but I was curious what it puts down on the dyno.

What do you guys think?

 

What's interesting to me, at least, is that your Cellmass maxes out around .85g @ 5800. Cellmass typically follows your torque curve. So I would expect 4800-5300 to be the max but for it to hold on through 6k. Btw, .83g is 100% Volumetric Effiiency. So anything over that is cooking. Just goes to show you that the MS4 wants to rev.

But your numbers of ~425rwhp sound about right with a cellmass around .85g.

By comparison, my 227 cam with TEA Stage 2 LS6 heads and a ported FAST 102 and Kooks 1-7/8" headers makes peak cellmass of .95g @ 6000 and carries to 7k and drops back to .87g at 6900 vs .79g for you at 6800. So you have a little less drop off even with the restriction. But my cam is much smaller and is still wanting to peak higher. You're also showing 95kPa MAP pressure @ 6800, so you're pulling some vacuum there. Ideally, you'd like to be around 99kPa that high.

So you would definitely benefit from less intake and exhaust restriction. An MSD Airforce and some 1-7/8" Headers into true duals or a 4" exhaust would probably open up 40-50rwhp.

You can also lean out your tune. You're around .82 Lambda, which is actually good for the dyno - means it'd be closer to .87 on the street. But for a hero pull, you could do a .87 or .88 and it'd pick up a bit as well. But running at .85 seems to make the car the fastest and is best for peak torque... a little leaner uptop for max power. But usually that's less than 10HP.

 

Thank you for the very interesting insights! If you'd like to take a peek: I attached my current tune to the first posting.

Do you think I should raise my rpm limiter to 7000? Looks like the power band just about peaks at 6700 but on a very nice plateau.

I was thinking about bigger headers, but then again this is not a project to squeeze out every last bit of power. I just want it to drive for fun on the weekends, no dragstrips. Maybe I'm going to have my LS6 intake opened up by TPiS to the 90mm TB, but I'm not sure yet. If I find a good deal on an MSD Airforce I might jump on it, but other than that actually I don't want to touch the hardware anymore. Down the road I might want the swap the MS4 for something milder that gives me torque around the bottom. I bought the car with the MS4 already installed, so I figured to make the best of it and just see if I like it. It sure pulls like crazy from about 4000 to my current limiter at 6800 but I think in the long run I would be more happy with a cam that has a wider torque band under the curve (=more useable power) and less peak power.

Now I haven't really touched the spark tables yet, tried to keep it very conservative. Do you have any advice on that matter? Where could I safely go without stepping into knock? I only fill my CETA with 102 RON fuel, which equals around 97 octane rating in the US.

 

I agree. Bigger 1 7/8" headers and a FAST or similar intake would net you quite a bit more. With a cam that big, I would most certainly raise the limiter to 7,000 rpms.

 

With the added octane, you could probably add 2-3 degrees. AFR combustion chambers are really efficient and don't need a lot of timing. So when I saw 25 degrees, I thought that looked pretty good. You could try 27 or 28 and see if it picks up power. I think it'd be okay with the added octane.

I would push the limiter to 7000 or 7200. The issue is you may drop off pretty fast with the LS6. Even an LS6 opened up for 90mm doesn't provide a lot. You really need a FAST 102 or an MSD intake. The MSD would give up more bottom end vs the FAST but carry better up top. So it sounds like the FAST 102 would be a better option and provide a good increase in the midrange over where you are now of probably 25-35rwtq.

The true duals would pick up more midrange torque as well and free up power uptop without having to swap the headers. The AFR 205s larger exhaust port and exhaust valve works better with a 1-3/4" header that most heads, so you may not see a huge advantage to swapping headers. But addressing the exhaust would free up midrange power.

 

This upcoming Tuesday I should finally have my "after" TPIS intake mod dyno sheet.
My combo is a very mild cam, CNC 799 headed, 368 incher but I sent the intake to Jackson @ TPIS back in December and had a few TPS(tune) issues but now is ready to get the tune touched up and spun on a stingy Mustang.
I know all the FAST/MSD guys will pimp those but for a factory look this seems like a pretty decent mod and I'm excited to see my increase.

 

Hmmm, 7000... the bottom end is completely stock, untouched. Are you sure 7000 is ok with it?

I'll try that, when I spend a few hours on the dyno to really dial in the VE, MAF and timing. On a load bearing DynoJet.

Again, 7000... stock bottom end? I'm not sure if I have enough faith in it.

Now about those intakes... yes, they would be very likely to net some more horses. But besides the intake you I would need a bigger TB, MAF, lid, fuel rails and at least for the MSD an LS2 water pump. All in 1,5-2k. I'm not ready to invest the time and budget to squeeze more ponies out of it. My injectors are very close to 80% DC at WOT so that would be the next thing to look at with another bump in power. Is the Walbro 255 gonna support that? How's my 10 bolt holding up?

My point is: I'm quite happy with what I have. Somebody will always be faster. I can live with that. There are other areas that I'd rather spend my rare free time and money on right now, like audio, paint etc. But I really appreciate the thoughtful advice about those intakes!

Wow, I'd be REALLY interested in the results, do you mind posting them here? Or do you have a thread where you post your results? Please let me know

 

You have an 02... the later rod bolts are good to about 7200 before I'd fret.

 

why do you say 0.83g is 100% ve? it seems that 5.7l : 8 x 1.3g/l = 0.93g.

 

Comes from Banish.

When you calculate it out, it's a little different based on the temp and pressure of air...

You can calculate it as PV=nRT (or n=PV/RT) where:
n = m/M (m=mass of air in grams,M=molar mass of air=28.96) mass of air = PVM/RT
P = pressure 101.3kPa
V = 0.70874 liters per cylinder (5.669 liter engine)
R = 8.314 (gas constant)
T = 294.15Kelvin (21 degrees C = room temperature)
so
m = (101.3*0.70874*28.96)/(8.314*294.15)
m = 2079.19/2445.56
m = 0.85 grams of air per cylinder. But remember that is only accurate at 21DegC and 101.3kPa. It will be different at different temps/pressures.

 

My limiter is set at 7,200 rpm's I believe. I am not a bit afraid of 7 grand.

 

well, no idea who "banish" is and of course its all dependent on pressure and temp., but at "standart" conditions air seems to weight 1.275 g/dm3. 0.85/(5.7/8)=1.193. so 0.85 would be the mass of air at a little above 20°c. oh, did you say 21°c? yes, you did. it only shows that 100% ve maybe is only 90% if you think about it.

https://en.wikipedia.org/wiki/Density_of_air

besides, the above is for dry air and interestingly humid air is lighter than dry air. would be nice to have a table with the mass of air at different humidyty levels. does anybody know where to look? i only know about this:

http://www.engineeringtoolbox.com/de...air-d_680.html

(how would water injection make more power?)

 

Greg Banish. He has put a lot of information out on tuning in general. I was just recalling what he had in his DVD. He had the 6L as .88g/sec and the 7L as 1.02g/sec in GM cellmass speak. It roughly works out. So I think those are pretty decent ballpark numbers on the GM calculated airmass.

So if I see a 5.7L above .83g/sec, it's working pretty well. Same for a 6L above .90g/sec or an LS7 up over 1.0x/g sec.

But yes humidity does change things. But there's no sensor in the car that accounts for it. So you just watch HP fall on a humid day as oxygen is displaced by water vapor.

 

Alright then, I'll give it a shot *fingerscrossed*

I'm still working on idle right now, it's quite a dive to tune that with the MS4

 

The MS4 may not carry past peak as well. I forgot it's only 1 degree advanced and the exhaust valve opens kind of late. But I'd run it to 7000 and see if it starts to drop off.

Did you get my PM on the idle?

 

Yep, I'll just try a run with the limiter raised to 7000 and see if the curve drops. Unfortunately my wideband just chickened out. So I'll have to fix that before attempting WOT runs into uncharted territory.

Jake, got your PM and sent an email

 

where do you get 102 ron gas? i thought aral didnt offer that anymore. btw, you hardly need it, i run my c5 at 15 psi on 100 ron and its fine.

on the topic of cylmass, where does the value we see (log) come from? do we know? is it given by the maf or somehow calculated in a different way. i just logged the c5 without blower and dyncylair is around 0.80g/s max in the 6000 rpm region. if you see 85 max my logg doesnt make too much sence, also because torque is supposed to peak at 4200 rpm stock. (my engine is completly stock.) i dont trust the cylmass data.

 

Aral still sells it: http://www.aral.de/de/retail/kraftst...offsorten.html

It's about $6 per gallon.

I just log cyl airmass.

 

in the meantime i have come accross some info (and i dont know if its correct or not) that airmass is calculated with the ve table being one of the inputs. if that is the case then it is of no use, because its based on some numbers you put in there. right?

 

I don't know. Where did you come across info on that subject?