Tom. M

Capricorn One....

That movie made me rethink almost everything I had been taught...

Except the Holbert record...That one was legit. ;-)

Later,
Tom
midlman@rennlist.com
bargain 87 S4 aT for sale $8999.00
89GT not for sale

Tom. M

.

Red UFO

Well I suppose maybe Jim Bailey was on that back lot when they 'made' the moon landing movie and the Holbert record. I wonder if Jim will ever come clean with what he knows. He should watch it, because if 'he knows too much'.

Porsche will send out their corporate assassins to silence him. Someone should FOIA the FBI with keywords 'Holbert record'?

Z

I don't know if Porsche would have risked using different cams for the record breaking run, especially since it was publicized like it was. If word got out, or someone found out, it wouldn't exactly make them or the new model that they were trying to make news with look very good at all. It's not like the speed record that they achieved was significantly faster than other stock S4s have been clocked at. It wouldn't surprise me at all if the cam change was made when the car was set up as an emergency response track vehicle.

Normy

No no no no no....

I remember a car magazine in 1987 [I majored in Aeronautical Science at Embry Riddle, with a minor in Car Magazine Reading....] talking about Al Holbert's record. They showed some pictures, and one of them was with the rear of the car jacked up and people working underneath. It's been a lot of years, but I'm sure they mentioned changing final drive ratio's in a quest for the best speed. I bet they swapped in a 2.73~

N!
'85 S2 5 Speed

mark kibort

the top end of the motor has a lot of hand written numbers on the bearing holders and cams. looks like it was a prototype engine. that has not been altered since the day it was built 18 years ago.

also the HP curves show none of the GT shapes. probably just a great running S4. remember, we went from 290ish with only cats removed.
after we got headers, we went to 305ish and after , fuel regs, fixing computer plug settings, no screens, vented air box, etc, we got 335rear wheel. I would say a lot of Hp would be reduced by use of the stock 2 screens. next time at the dyno, remove yours and let us know


Mk

Z

Mine have been out for years already. There was some difference in power from removing them, but not much.

Jim bailey - 928 International

The largest loss of power running at Bonneville is caused by the altitude 4,200 feet above sea level and the resultant loss of about 12% of the "normal horepower " . Traction is poor as well much like driving fast on a gravel road . I would expect that Holbert and crew would have shaved the cylinder heads to bump static compression to compensate for the higher altitude . They went there to set a record knowing that there would NOT be a teardown or inspection since they had hired the people certifying the speeds .

heinrich

Removing the screens made a measuable power difference on my car, but I elected to return them since I'd rather have 2hp less and no chance of ingesting a Subaru .....

Z

If that Subaru makes it past the air filter, the screen isn't going to stop it either.

The purpose of the screens isn't really to keep stuff out. If you think about it, why would there be a screen on the bottom then? To keep stuff in? The screens are there to diffuse the airflow and provide for more accurate metering by the MAF sensor. The way that the air is routed into the MAF by the air intake system on a car can have an effect on the metering accuracy of the MAF sensor. The type of MAF sensor used on some types of other cars uses a sampling tube in the sensor, and that type of MAF is apparently more suseptible to that. The screen on the bottom helps with reversion pulses that the sensor may be vounerable to. A reversion pulse from the intake moving back out through the MAF would be air that's then been measured twice. The result would be that the system thinks more air has entered the engine than actually has.

The Corvette had a MAF with screens very similar to those in the 928. It was found that with the way the air flows through the intake tract, the screens really weren't needed to diffuse the airflow in that application. The newer models of Corvette then started to come with identical looking MAF sensors as the ones in the earlier cars, only now with no screens in the new ones.

mark kibort

compression on all 8 cylinders is and has been a solid, 180psi, with almost no variance between cylinders.
even though you have a 15% or so air density loss at 4200 feet, there is also a reduction in drag of even greater impact as the speed goes up. most of the hp at the top speed is required to overcome drag. (goes up with the square of the speed) for top speed, anyone would sacrafice 15% hp to gain 50% less drag at a certain speed (as an example)


MK