Modded L67 TB for L36--NOW with Gutted Airbox! - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 05-18-2007, 02:31 PM   #21
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I went ahead and put the GAB (gutted airbox, how ‘bout another acronym :o )--with stock air filter--on the modded L67 TB and re-did the VE tune…



This is a significant increase over the previously reported numbers in this thread, and it is clear the bigger TB needs a less restrictive intake (heck, previous mod levels may have benefitted from this, I don't know). Calculations now put the car at:
Peak crank torque: ~305-310 ft lb at ~4200 rpm
Peak crank hp: ~260-265 hp at ~5200 rpm

IPW'* are telling me that, at WOT with PE on in the 5000-5500 rpm range, I'm now at about 97% of injector duty cycle…luckily, I’ve got L67 injectors on the way from BillBoost37, so I can continue modding.


I can see there have been requests for how I’m coming up with these hp and torque estimates:
Quote:
Originally Posted by big_news_1
I'm curious how your tuning and VE graphs translate into quantifiable numbers.
The “quick and easy” method for hp estimation is to analyze Brake Specific Fuel Consumption (BSFC), expressed in lb/(hr-hp), which is related to thermal efficiency:
http://www.epi-eng.com/ET-ThermEff.htm
http://www.answers.com/topic/brake-*...el-consumption

BSFC = observed fuel consumption (lb/hr) / horsepower

Lower BSFC is more efficient, with a typical n/a liquid-cooled engine coming in around 0.44 to 0.45; 0.53 is pretty bad, and 0.4 is really good.
(Note: air-cooled engines, power-adders such as turbo or */c, high intake air temperatures, knock, etc. tend to decrease efficiency and increase BSFC, while cold air temperatures, optimized timing, intercooler, aluminum heads and blocks, CAI’*, reducing underhood temps, multi-valve configurations, headers, reduced ECT’*, etc. tend to do the opposite.)

So what is the BSFC on my car? In stock configuration (assuming the published 5200 rpm peak hp number of 205):
100% injector duty cycle at 5200 rpm = 21.2 msec
Measured IPW: 15.8 msec
Calc Injector duty cycle = 15.8 / 21.2 = 0.74 (or 74%)
Max injector flow rate: 22.4 lb/hr
Calc fuel consumption @5200 rpm = 0.74* 22.4 lb/(hr-injector) * 6 injectors = 99.9 lb/hr
BSFC = 99.9 lb/hr / 205 hp = 0.487 (or 48.7%)

This seems pretty reasonable for an n/a car with cast iron heads and block, and nothing done to enhance engine cooling beyond an auxiliary tranny cooler, 180 T-stat and some fan settings in the PCM.

Now, on the (admittedly large) assumptions that:
1. The factory torque/hp curves were done under conditions that would derive similar thermal efficiencies to the engine mounted in my car; and,
2. My thermal efficiency hasn’t changed throughout my mods

Hp should be directly proportional to observed fuel consumption (more specifically, IPW), as follows:

Hp (@5200rpm) = IPW (in msec) / 21.2 msec * 22.4 lb/(hr-inj) * 6 inj / 0.487 lb/(hr-hp);

Which reduces to:

Hp (@5200rpm) = IPW (in msec) * 13.0 (hp/msec)

I haven't changed timing since the PEM. Also, all my testing has been done with the same cooling system, the same fuel brand, over the same "road course", and in a very narrow range of outdoor temps (70-75 F)...so I've done all I can to ensure no change in thermal efficiency.

Charting it out:

Mod level......Meas avg IPW(@5200 rpm).....Calc bhp
Stock..............15.8........................... ...................205
Plus PLIM......16.6.................................... ..........216
Plus PEM.......17.3.................................... ..........225
Plus L67TB...19.3...................................... ........251
Plus GAB.......20.6.................................... ..........268


I have another method that relates VE to torque and hp, but it will take me a while to explain that one. :P

Of course, my estimates need verification with a real dyno...I'm working on that

First off, the factory probably generated their hp and torque data on an engine stand in a controlled temperature room, rather than in a car; this likely would improve thermal efficiency on the order of 10-15%, which would translate directly to a good 10-15% drop in actual bhp versus my estimates. If I could somehow do a brake dyno on this car today, I would expect to see results somewhere around 265-270 ft-lb torque at ~4200rpm, and 225-230 bhp at ~5200rpm (compared with stock numbers I would expect to have been 200-205 ft-lb @4200rpm / 170-175 bhp @5200 rpm).

Second, of course, I expect a 20-25% drivetrain loss. So if I were to wheel dyno this car today, I would expect to see results somewhere around 205-210 ft-lb torque at ~4200rpm, and 175-180 whp at ~5200rpm (compared with stock numbers I would expect to have been 155-160 ft-lb @4200rpm / 130-135 whp @5200 rpm).

Yeah, those numbers ain't so flashy; but then again, I haven't moved on to the "big money" mods yet
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Old 05-18-2007, 06:43 PM   #22
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i need to subscribe to this thread.. the results are outstanding
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Old 05-18-2007, 06:45 PM   #23
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I am very interestd in seeing a set of ER Rockers on your setup. I know that it would take care of that drop off. And you would make power til 6000
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Old 05-18-2007, 07:22 PM   #24
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Quote:
Originally Posted by TJ'sblackbonne
I am very interestd in seeing a set of ER Rockers on your setup. I know that it would take care of that drop off. And you would make power til 6000
I've got the rockers in a box in the garage. After I put on the L67 injectors, they're next.
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Old 05-18-2007, 07:31 PM   #25
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You are going to love the rockers, well atleast i know i did. I can not wait to be able to do some more engine mods to my car. As soon as the trans is in and tuned, and i get some solid track numbers of where i am at with the new trans, then let the engine mods begin Thank you for all these info, it has been awesome.
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Old 05-18-2007, 08:20 PM   #26
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Agra, if your car is making 260hp at the crank I will be astounded. Not saying it'* impossible, but I don't think we've ever seen a car with such minimal mods making that much power. I truly hope you get numbers that high. You need to get that car on a dyno ASAP, because if you can back up your VE graphs with numbers it will change the focus of many L36 modders in the future.

I don't know if I've been this excited about a car since I put in my cam! I'm intrigued by the estimations so far, but I really want to see hard numbers.
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Old 05-18-2007, 10:24 PM   #27
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Quote:
Originally Posted by big_news_1
Agra, if your car is making 260hp at the crank I will be astounded. Not saying it'* impossible, but I don't think we've ever seen a car with such minimal mods making that much power. I truly hope you get numbers that high. You need to get that car on a dyno ASAP, because if you can back up your VE graphs with numbers it will change the focus of many L36 modders in the future.

I don't know if I've been this excited about a car since I put in my cam! I'm intrigued by the estimations so far, but I really want to see hard numbers.
Like I said, I really expect more like 230 bhp (180 whp) max...but a man can dream

Even so, this would represent somewhere north of 25 added hp over stock for around $150 in modded stock parts. Aside from a few ideas I have for the UIM, mods start to get relatively expensive from here on out (modded stock rockers, modded heads, 105# springs).

I'm hoping to get some dynos sometime in July or August...best price I've found around here is $90 for two pulls
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Old 05-19-2007, 12:31 AM   #28
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If you make 180WHP on stock valvetrain then you have my most respect. I truely hope so. I cant wait to see some real numbers. My ultimate goal would be to break 200whp on rockers. I hope it happens. Congrats on everything so far, and thank you for all the data and ideas.
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