[Archived]

We had an unmodified 475 HP 8V92 for 15 years and drove it all over the country. The only time the lack of low RPM power was even worth noticing was pulling away from a stop, pointing uphill,at high elevation. Apart from lack of off the line performance there was more black smoke than usual upon acceleration. Once the RPMs started to climb the coach performed well.

At this point I seriously doubt if you would want to face the cost of making that mod to the engine. Our 8V92 coach always did well compared to the Series 60 in a drag race because when paired with the 5 speed Allison it hung in the gears longer (unless the Series 60 driver was manually shifting) and the end result was it was equal to or better than the newer engines because they were typically in heavier coaches offsetting the advantage of the low end torque they seemed to have.

Yes I drag raced a couple of guys with newer coaches. Yes I beat them. I could also pull hills at the posted speed limit. But until I got to about 1500 RPM from a dead stop the coach performance was underwhelming. At highway speeds there never was an issue. If you want performance change the differential gear ratio.

Coloradobus lives in Denver, they have an 8V92 and I would like their opinion because they have had a range of coaches.

[stephen]

Have a Silver 8VTA in my 1991 and wouldn’t know if underpowered. Just pull flats and some hills around West Texas and Hill country. Always have Ford Edge and FordSupercrew F150 4WD towing behind. It gets up and goes with the traffic. Only other thing I’ve had to compare was 35 foot Holiday Ramblers with V10 Ford motors. No comparison. The 8V92 would eat those things for breakfest. Of course the 4 to 5 miles per gallon is an eye opener with the 8v92.

[Rick & Denise]

Dental, if you feel you are too slow off the line, get your injectors checked. We had one marginal injector on our 8v92 and it really slowed us down from a standing start and on hills. Changing that injector for a good one made all the difference. As Jon said, slow and smokey at elevation, but otherwise we were okay without any modifications for many years.

[Archived]

I really don’t understand this I know they had a ugrade to change to the DDEC 111 from the 11 in that time frame but a blower drive ratio would not change the turbo boost .

If you want to bring a 8v92 to the same party with the 60 series you do that with a charge air cooler that wakes one up and doesn’t cost that much to do IMO

[Greg]

thank you all for your comments. A higher blower gear ratio only changes your boost i you move the sensor from above the blower to below it. Out of curiosity what is a charge air cooler?

[Sherry]

A charge air cooler is to air what the radiator is to coolant.

An 8V92 uses a coolant to blower / turbo air to remove heat from the air and absorb it with engine coolant. The air temperature rises as air is compressed and reducing the air temp going into the engine makes for a denser air supply which translates into more oxygen for combustion which allows more fuel, which creates more HP.

On the Series 60 the turbocharged air is being cooled through the charge air cooler prior to entering the intake manifoild.

The intake on the 8V92 is essentially the “box” between the cylinder banks and beneath the blower and that area is under pressure so it pushes air into the cylinders at the bottom of every piston stroke.

[David]

All the 550 Hp 8v92 DDEC IV used a CAC I never saw one with a aftercooler the 8v92 was the first engine to use the CAC they have been around and used on the 8v92 since 1980 as a option to me the aftercooler inside the block was a joke it is not large enough to do much good but it helps a little

[John]

Our Silver 92, 500 hp has good power. As Jon said above we have had several Series 60s with Allison 4060 6 sp auto transmissions utilizing rear gear ratio 4.56. One in a 1999 XL shell w/2 after market slides, another in a 2001 XLII shell w/ 1 Prevost installed slide, and the third one in a 1999 H3-45 slide-free. Both stainless coaches weighed in just over 50,000 lbs, and the “H” , no slide, weighed just over 51,000, but had the best aero-dynamics. Out of the three 45 footers, the H3-45 had the best snapped off the line, good mid range power, and the best pulling power. It did have 5000 miles on it when we bought and sold it with 110,000. Both XLV and XLII 45 had less than 42k miles.

Our current coach, a 41,000 lbs 40 footer, 1992 8V-92 equipped with Allison HT 755, 5 speed transmission turning a 3.58 rear end. When we bought it in 2009, it had 62,000 miles on it, and currently has 9300 . It pulls the grade on I-70 heading west out of Denver at 35-38 mph in 2nd gear , and tows same car as the H did, which pulled the same hill at 35 in 3rd. Off the line, the H3-45 did better than the 2 stroke at our altitude, but at or near sea level, the 8v-92 excels.

Dental Guy, when did Prevost offer this blower gear change. We have no open bulletins

[Archived]

I don’t understand how changing the blower ratio from 1:95 to a 2:11 ratio which I can not find DD ever made a 2:11 the 2:05 which they did make will change the turbo boost, as the by pass blowers on a 8v92 start to free wheel when the turbo boost reaches a certain point of pressure

I have been unable to find out anything about a 2:11 drive blower drive increasing the turbo boost it takes fuel and exhaust heat to increase turbo boost on a 92 series different hot housing can change the torque range from low,middle or high end on 92 series fwiw

[Davy]

Coloradobus,

I have a Prevost bulletin dated September 1995 with two sets of reference numbers:

From Mira Loma I have T-976 and F-909

From Prevost car Texas I have 8176858460

Best regards,

dentalguy/whiskeybill