its a little turbo as well as it appears to be internally gated (personal preference - i like EG) and id also want to know the type of BOV.. i mean other than that i dont see what would be wrong with it.
It'd be nice to know some specs on the turbo they put in there. I think T25 commonly came in 45 55 and 60 trim.
Anybody have compressor maps for the T25 they're hard to come by? If I were you, I'd rather know how efficient it will be before handing over the cash. And from my recollection this turbo is too small for our displacement engines. It begins creating boost just outside of idle, low end torque no top end.
Just a few maps for thoughts...keep in mind this is my map for a 2200. Tick's from the left to right (2000, 3000, 4000, 5000 RPM). The DOHC will have a greater estimated volumetric efficiency than the OHV, assume 90% rather than 85% which I did for these graphs (pretty much scale the points to the left for corrected air flow), and a higher redline so add another tick at 6000.
Notice how past 4000RPM you are already at the choke line, not to mention you miss the center island of efficiency over 8psi...
T25 (50 trim)
T25 (60 trim)
And some more maps for thought - A T3 super 60 with a 2200 (again ecotec can shift points slightly to the left for greater VE). may of the t3 and t3/t4 hybrids are right in the sweet spot for our displacement and flow characteristics.
Turbo readup - please don't just buy a kit without a bit of research..it makes baby jebus cry. I've oversimplified this post, see the links below for all of the formulas and work behind mapping the points above and turbo selection:
Garrett's guide to turbos
Common T compressor maps
Another good resource for formulas
Digging up PJ's old guide
Volumetric efficiency is not constant at all RPMS. Using values like that will grossly oversize your turbo.
fortune cookie say: better a delay than a disaster
I skimped out on that calculation because I don't have cfm tables relative to rpm, an accurate dyno sheet of a stock 2200, a flowbench to measure actual airflow (or the brake specific fuel consumption value of this engine to even get an estimate airflow). If you use crank output of 115HP@5000rpm and the below efficiency formula you get over 100% VE which is impossible. I can't use the second formula because I don't have an actual CFM rating. Using the theoretic max cfm rating at rpm relative to the P&P head flow chart from patriot wouldn't be accurate either.
So either I'm doing a miscalculation or the first formula is inaccurate, and the more I estimate the less sure I am of the accuracy of the results. If you can help point where I'm wrong it'll save me a big headache later today when i look at this again.
VE = (Horse power X 792001.6) / (Atmospheric Pressure X Compression Ratio X Displacement in cc's X RPM)
or
Ve = (3456 X CFM) / (Displacement in cc's X RPM)
set both formulas equal to each other, take out common variables and you get:
(HP X 792001.6) / (Atmospheric Pressure X CR) = (3456 X CFM)
CFM = (HP X 792001.6) / (AP X CR X 3456)
= 199.2 CFM @ 115 HP, 14.7psia, and 9:1 CR ---> which is way too high for the stock engine, it's higher than the flowbench rating of the patriot head I've got on it.
Estimating 95HP peak (wheel instead of crank) nets you 164CFM (a VE of 84% at peak torque and pretty near redline)
plug everything back in the original equation the numbers all work out. Was the whole issue using crank HP relative to WHP?
When doing motor evaluation, you MUST use bhp, NEVER whp. I'm not sure where you got those equations, but I've never seen CR used in a VE calculation unless the intake/exhaust pressure ratio was also considered...
Also, how are you planning to use a head's flow-bench #s to determine motor CFM? Since you can't assume the values from a single lift point, you would have to plot them, fit a polynomial, and then apply the mean value theorem for integrals to even get close...and even then, it's not like you only have one cylinder intaking air at a time...
My computer with all my LN2 info is down, but maybe Jack can get you some rough VE estimates on his desktop dyno.
Next time someone with a bolt-ons motor goes to the dyno, PLEASE log a mass airflow meter along with wideband readings.
fortune cookie say: better a delay than a disaster
Thanks notec, I needed to know where it went wrong. This is the kind of information we need in a boost forum sticky. And the formula thing, that is what I get for trying to get information off the internet, try a different online source and you get different information. Really need to get a book on this..
My current ICE textbook has plenty of formulas...how in depth do you want to go?
fortune cookie say: better a delay than a disaster
VE information isn't so hard to come by. GM supplies it with every speed density calibration they hand out.
While the numbers may be off a bit the curve is definitely going to be correct. Start with GM's number and work to correct them.
-->Slow
