MelloYellow

I'm continuing to look at the new 62-1 kit from Cerra Racing. Their early dyno runs shut down around 5500rpm's and starts to fall off kinda quick after that. Unsure why right now and am giving them the benefit of the doubt for now.

My goals are 550rwhp with a 216/224 114 Cam, 9/6:1 Gasket, LS6 Intake & Bolt-Ons. Will do 42# and Fuel Pump Upgrade. I believe the 62-1 can handle 10psi. But at higher RPM's, what kind of lb/min flow am I going to be seeing? How should I read this compressor map? It will be dual intercooled and am hearing only 10* above ambient at 6psi.

I want to make sure the 62-1 can handle 6000rpm shift points. Whatcha'll think? I don't know how to read the compressor maps yet or how to judge the efficiency or get a feel for how much heat/detonation prone the 62-1 might be at 8-9psi and 5500-6000 rpm! Don't want to detonate up top.

http://www.turboneticsinc.com/comp_maps/Fig10.gif

This kit sounds like it might be the right one for my goals, but if I need to wait for a T72 or T76 and new hood, I will. I don't plan to grow above the stated 550rwhp goals or upsize the engine later.

Thx!

<small>[ September 15, 2002, 10:17 PM: Message edited by: MelloYellow ]</small>

red ws6 99

You wont make it with that turbo it tops out at 62 lb/min which corresponds to maximum fwhp of ~ 620 and thats at 65% efficiency and 20 psi. So say 15% loss driveline thats a maximum possible of around 530-550 rwhp. But since you are in such a low efficiency range of the compressor map you will be creating tons of heat. You need a lot more turbo if you want to run low boost and have good efficiency.

Gary

MelloYellow

Shiite. I was thinking the same.
Guess I can chill and wait to the T72 and a hood bulge for the Turbo..

But...
The 62-1 Stock '02 Z06 put out 500rwhp/520rwtq at 7.1psi I believe at 10.6:1 ??

http://www.cerraracing.com/crturbokit1.cfm
http://forums.corvetteforum.com/zero...=380003&page=1

Also, Isn't the fwhp rating on the 62-1 725fwhp?
https://ls1tech.com/ubb/ultimatebb.p...;f=20;t=000928

Is there a way to convert 'Pressure Ratio' on the compressor maps to 'Boost'?
How do I convert LB/Min to Horsepower? Doesn't the engine and mods have a lot to do with how that LB/Min translates to HP also?

Also, if the last post was true, how were the 60-1 TurboTech kits putting out over 500rwhp?
http://www.turboneticsinc.com/comp_maps/fig9.html

<small>[ September 13, 2002, 09:14 PM: Message edited by: MelloYellow ]</small>

red ws6 99

Pressure ratio = (atmospheric pressure+ boost pressure)/ atmospheric

lb/min x10 = fwhp this assumes best case for everything. This seems to work pretty good at least on the Incon cars (lot higher efficiency setup)

You can make more than what is on the compressor map to a point. You will either have less efficiency (most likely), need high pressure, or a higher rpm that what the manufacturer recommends. This all leads to a poorly designed system (low efficiency, high heat) or a turbo thats going to basically be abused a lot.

Yes mods make a difference, but the compressor maps give you the maximum possible.

Gary

<small>[ September 14, 2002, 11:41 AM: Message edited by: red ws6 99 ]</small>

MelloYellow

Making sense, thx!

AlienDroid

I'd go for the larger turbo <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Heat is bad

<img border="0" alt="[guns]" title="" src="graemlins/gr_guns.gif" /> heat

I think it would be best to run the T72 at a lower boost level then max out the 62.

You can compare air flow capabilities for the turbos at different pressure ratios to see if your turbo can work at x max engine rpm. But I don't remember the formulas and I don't remember where I read them. I'd go T72 if I were you, don't max out a turbo and you will have less problems with tune.

<small>[ September 14, 2002, 10:03 PM: Message edited by: AlienDroid ]</small>

MelloYellow

Agree, this seems to be the best way to go. Was just trying to see if it would work with the Stock hood, but it won't. 2 new hood designs are 1-2 months out for the T72 kit.

Still trying to make sure I fully understand the compressor maps. On the left hand side where they say 'PRESSURE RATIO P2C/P1C'.. what is a P2C and a P1C? Does 1.0 = 1 Atmosphere, NO Boost? 2.0 = 14.7psi? That would mean 1.6 = 9psi and 1.4 = 6psi. I must be doing something wrong, cuz in the lower Pressure ranges, the T72's efficiency is horrible. If we are under 10psi, is this the right turbo? I'm missing something here.. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> I must have the Pressure Ratio concept all wrong? LOL

MelloYellow

Found this. Seems to be filling in my missing piece. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

"The y-axis shows your Pressure Ratio. The Pressure ratio is simply the absolute pressure coming out of the turbo, divided by atmospheric pressure. Boost gauges show relative pressure, meaning that they show pressure above absolute pressure(atmospheric). For example, your tooling along going 120mph with your foot to floor, your boost gauge show 14 psi(or .97 bar). The pressure ratio is [ 14psi(your boost gauge reading)+14.7psi(atmospheric)]/14.7psi(atmospheric) = 1.95 pressure ratio(PR)"

Even using this formula, I don't see that many of the turbos are as efficient at lower psi boost levels of 5-10psi. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> The T76 looked the best, but still?

<small>[ September 15, 2002, 10:18 AM: Message edited by: MelloYellow ]</small>

AlienDroid

One thing you need to take into account is that at the same compressor efficiency, like say 75%, at 1.0 pressure ratio compressor discharge temps will be around 100 degrees F, but at 2.0 the same 75% efficiency will yield temps of around 250 degrees F. This is why turbos seem to fall out of the high efficiency range as pressure ratio goes down. In reality it's because temps are staying nearly the same at first until pressure ratios go above 1.5, where discharge temps start to skyrocket. temps go up naturally as you compress more air into the same volumn. So in other words, 45% efficiency at 1.5 pr is less troublesome then 80% efficiency at 3.0 pressure ratio. The only thing we care about with efficiency are air temps.

Airflow rate NA = (cid * rpm * 0.5 * volumetric efficiency)/ 1728

so Airflow rate = 347 * 6800 * 0.5 * 0.85 / 1728
= 580 cfm.

This is how much air your motor needs at 6800 rpm for its NA application.

Now let's say you want to run 7psi of boost.
PR = (14.7+7)/14.7 = 1.476

So at max rpm you would need 1.476 * 580 cfm or 856cfm

I'm looking at two compressor maps of the 60-1, one is in cfm and one in lb/min.

It has a max of 825cfm and about 64 lb/min. This is kind of a rough geuss but I get about 12.9cfm = 1 lb/min of air. I did this because I only have lb/min graphs of the t72 and t76

If you look at the compressor map of the 60-1 you'll see that you will be way out of the best efficiency range at 6800 rpm at 1.467

but you might notice at 2.2 you have a lot more cfm range, but if you calculated your cfm level at 2.2 you'd need a lot more then 856cfm, so can see why you wouldn't make much power at that high rpm at any boost level.

T72: Yeah, 1.467 is way below the comfort zone of the turbo, remember lower boost levels can live with a lot less efficiency. If you look at the compressor maps you'll notice that the turbo rpm lines at the top, at the highest turbo rpm, the line almost becomes vertical as it moves down, that is the turbo's max flow rate. Pick a pressure ratio like 1.467 or 1.5 and draw a line on the map from the surge limit to where the turbo rpm line from the highest turbo rpm would be. Notice as you move up in air flow rate the turbo's rpm increases. The last line is the fastest you are going to spin it.

Now to see if we can get 856cfm on the t72. 856/12.9 = 66.35lb/min. Look at your compressor map and look for 66.35lb/min on the bottom and 1.5 on the left. You will still be way outside the best efficiency range, but notice that you won't be working the turbo very hard. The t72 will spool up really fast and you'll make peak hp at a lower rpm. the map I'm looking at wasn't labeled very well.

T76: look for 66.35lb/min again and 1.5. You are still in a less efficent range then you might want but then again you won't be making max hp at 6800 either.

I recalculated for 6000rpm at 1.5 pressure ratio. 770cfm. or 59.5 lb/min. It looks pretty good on the t76 map. Try 2.0 pressure ratio. 79.3 lb/min and check it out on the map at 2.0 pr, it still looks pretty good.

If you want to check out your efficiency at every rpm range from the map you just need to calculate your cfm at different rpms and mark the cfm(or lb/min) on the graph at your pressure ratio.

but at 1.5 pr(7psi) your temp range between 80% and 45% eff is going to be somewhere around 160-230 degree temps in the pressurized air. Not a big deal compared to the temps the folks that run 18+psi have to deal with.

<small>[ September 15, 2002, 06:37 PM: Message edited by: AlienDroid ]</small>

MelloYellow

AlienDroid:
Thx much for taking the time to write that! That helps a lot. I understand most of it now.

Is there a good way to determine how much increased heat we'll see from a given turbo at different boost levels/rpms/efficiencies?

Do you have any better compressor maps of the T72 and T76? The ones at the TurboTech site are hard to read and not marked well. Thx!! email mjarnold@vsecurenet.com

Also, FWIW, I'll probably try to shift around 6000-6200 to keep the temps down. That would be smart, right? Also below the surge limit, I'm not spooled to full boost?

<small>[ September 15, 2002, 10:11 PM: Message edited by: MelloYellow ]</small>

AlienDroid

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>AlienDroid:
Thx much for taking the time to write that! That helps a lot. I understand most of it now.

Is there a good way to determine how much increased heat we'll see from a given turbo at different boost levels/rpms/efficiencies?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">no prob <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

I have a chart right in front of me that guesstimates it. At 1.0 pressure ratio (0 boost)pressurized air temps will be almost the same at any efficiency, near 100 degrees F (just an assumed starting point) but remember these are temps before the intercooler. Without an intercooler a general rule is to avoid going below 60% efficency on the turbo, but with an intercooler you can go much less then that if you have to. The efficiency of an intercooler measures the percent of the heat gained from the turbo that is removed from the air before it reaches the intake. With an example intercooler with 75% efficiency let's say you are running 7 psi or 1.5 pr and your worst compressor efficiency is 50%. Your compressor outlet temp will be about 225 degrees F(from table) and let's say outside air temps are 90 degrees F (remember intercoolers can't lower intake temps below outside air temps). 75% of this extra heat will be removed by the intercooler or about 101 degrees of the 135 degree increase, leaving a total temp of 123 degrees F going into the motor.

Only boost levels and compressor efficiencys will determine temp changes, not engine rpm.

<small>[ September 15, 2002, 10:24 PM: Message edited by: AlienDroid ]</small>