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1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 07-26-2005, 05:18 PM   #11
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Good to see you on the board 2seater, this is marcus (trofeo73 on bca)!

I am going with a fastchip setup on the trofeo, as that seems to be a good supplement to an safc, ect.
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Old 07-26-2005, 11:27 PM   #12
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My 88 and 90 LN3s definately had a 124 mph cutoff (cars came with "H" rated tires). Not sure when this started. Cars with "*" rated tires from the factory have a 112 mph cutoff. Is just two bytes in the PROM (one for cutoff and another for restore).

Of course few "C" 3800s reach ever 124 mph (206 kph ?) so is not usually an issue.

Suspect that is a US regulation, do not know if was on Canadian cars.

RPM cutoff is at 6k and no 3800 should reach that except by accident, certainly won't be making any power.

Is not just one thing: ded cam, limited intake, restrictive exhaust (particularly the rear manifold which is terrible, suspect was designed so that the engine could be installed with the manifolds already in place). All need to be improved to make more power and particularly the camshaft.

Keep in mind that the "C" engine was designed for a 55 mph national speed limit and 1600-1900 rpm highway cruise in o/d-lockup. 30+ mpg there but declines as speed increases. Max torque (210 lb-ft) is at 2000 rpm and is really pretty flat out to 4500 with 166 lb-ft and 165 hp at 5200 rpm being the hp peak but with torque dropping off fast.

The Series II engine was considerably improved and came out after 70 mph speed limits were back with HP taking a big jump not because there was more torque available but because the curve was moved up the range.

182 hp from a LN3 is certainly possible if the intake and exhaust are cleaned up but suspect the most benefit would be from about a ten- fifteen degree more duration cam.
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Old 07-26-2005, 11:39 PM   #13
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What can be done for the intake? or do you mean a CAI or something? and assuming that youve got an intake and cleaned up the rear manifold with an exhaust, would chip make a noticeable difference? what do you think the hp increase would be?
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Old 07-27-2005, 11:14 PM   #14
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This was GM Tuners reply to the question of a speed limiter and Bonneville'*:

"The bonnevilles typically have a top speed limiter set at about 107-120 mph."
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Old 07-27-2005, 11:41 PM   #15
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Quote:
Originally Posted by phoenix_flame220
What can be done for the intake? or do you mean a CAI or something? and assuming that youve got an intake and cleaned up the rear manifold with an exhaust, would chip make a noticeable difference? what do you think the hp increase would be?
I can only relate what the results were on my car for the first mods. This is a 1990 LN3. I can read air flow from the MAF. Bone stock the maximum air flow observed was 125 grams per second. I derived a crude formula of 1.32 x gr/sec = hp. I made a CAI with K&N cone filter, opened up the restriction inside the rear exhaust manifold outlet, removed the cat. from the exhaust system (straight pipe), 160 degree thermostat and a Fastchips prom optimized for 93 octane. The resulting air flow reading averaged about 137 gr/sec, or an increase of approx. 16 hp under similar conditions. This yields just under 181 hp total. I believe the majority of the better air flow is from improving the in and out from the engine. I never tried it without the chip. Injector pulse width ran up to about 21 ms at 5000 rpm, or about 85% duty on the stock 18.8# injectors (nominal). This should be enough fuel for about 190 hp and the chip is set relatively rich. Fuel mileage dropped about 5%. These figures should not be taken as gospel, the initial calculation is based on the stock 65% engine efficiency, and improving air flow in and out may improve the efficiency slightly ( the cam does most of that), but the figures are valid if taken in the right context.
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Old 07-28-2005, 11:20 AM   #16
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Quote:
Originally Posted by 2seater
I can only relate what the results were on my car for the first mods. This is a 1990 LN3. I can read air flow from the MAF. Bone stock the maximum air flow observed was 125 grams per second. I derived a crude formula of 1.32 x gr/sec = hp. I made a CAI with K&N cone filter, opened up the restriction inside the rear exhaust manifold outlet, removed the cat. from the exhaust system (straight pipe), 160 degree thermostat and a Fastchips prom optimized for 93 octane. The resulting air flow reading averaged about 137 gr/sec, or an increase of approx. 16 hp under similar conditions. This yields just under 181 hp total. I believe the majority of the better air flow is from improving the in and out from the engine. I never tried it without the chip. Injector pulse width ran up to about 21 ms at 5000 rpm, or about 85% duty on the stock 18.8# injectors (nominal). This should be enough fuel for about 190 hp and the chip is set relatively rich. Fuel mileage dropped about 5%. These figures should not be taken as gospel, the initial calculation is based on the stock 65% engine efficiency, and improving air flow in and out may improve the efficiency slightly ( the cam does most of that), but the figures are valid if taken in the right context.
Somebody really knows what they are talking about!

So our stock injectors are only good for 190hp?

What about the maximum the MAF can read.. i thought it was 125gr/sec, but obviously that isn't it. I know it'* less than the 92+, maybe like 25 or 50gr/sec les?
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Old 07-28-2005, 10:49 PM   #17
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The general rule of thumb for fuel requirement with a normally aspirated engine is about 1/2# of fuel per horsepower per hour and a little more for a boosted engine. It will vary a little from engine to engine depending on the BSFC or Brake Specific Fuel Consumption. It works out to two hp. for every pound of fuel per hour, and about 1.75 hp for a boosted engine. This will get you in the ballpark and tune from there. The stock Bosch -901 injectors in the 3800 engine like mine theoretically could supply up to about 225 hp, but they would running open all the time at maximum demand. Conventional wisdom suggests the injectors be sized to provide for maximum demand using 80%-85% duty, or open that percentage of the time to prevent overheating and compensate for varience jn the flow capacity of the injector. Most injectors can vary by 1%-3% from the nominal flow rate, and of course the injector must be clean. My personal preference is to size the injector closer to the maximum capacity, like 90%or slightly higher. The reason being, an injector dribbles as it opens and closes, the spray pattern is only correct when fully open, and an injector that is way too large will have an extremely small pulse width, or open time, at low demand, so in many cases idle and low speed performance is rougher. Good chip tuners can make big injectors work, but I am talking about the stock chip. For street driven car, the injectors are just loafing along, and only see maximum demand rarely, so I guess I am inclined to use up some of their life running closer to the limit once in a while.

My '90 ECM can read up to 170 gr/sec of air flow. Oddly enough this works out to very close to the maximum flow capacity of the injectors, a pretty well balanced system IMHO. My opinion would be 200 relatively safe hp could be fed with the stock injectors and a little more if the fuel pressure is turned up to get more flow capacity. For example, if the pressure is turned up to a base of 50 psi, the injector will flow a little over 20#/hr. While tuning for my turbocharged application, I found the stock system was able to run 24# injectors acceptably, but the stock chip got very close to bottoming out when the flow was raised to close to 26#. The BLM reading was down to around 100 at cruise speeds, and that seems about as low as it will go. GM Tuners did a chip for me and I am now using GN injectors with the fuel pressure turned down a little to deliver 28#/hr and am now pretty close to where the fuel delivery needs to be for 8#'* of boost. BLM is reading 106-110 at cruise and delivers 26 mpg in my daily commute of 70 miles. The chip will be adjusted to correct the BLM reading closer to the desired 128 and back down the timing a few more degrees. New 30# injectors are on order and the tuning will be changed after they are installed. Sorry for the rambling but I hope it of some use.
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Old 08-02-2005, 11:44 PM   #18
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I needed to post a correction to what I mentioned previously. I have found not all injectors can be pushed to very high duty cycles. The stockers would go almost 100%, or 24 ms at 5000 rpm, but the Accel 30# refuse to go beyond approx. 87%. Maybe an injector driver problem in the ECM? Still investigating.
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