James Bailey

I was tempted to say you obviously never held the gas pedal down long enough.....but that would have been unkind Oh and at Nardo the neutral speed is 150 mph any more and you MUST be turning all the time which slows the car !! and makes it a constant sweeper despite the banking. An endless 12.5 KM "corner".

mark kibort

yep, and that car was only near 290rwhp .
remember Bonneville was probably mainly limited by wheel slip, as the air density at 4500ft, is 15% less than at sealevel, which is a big deal at that speed. so, they even did it in that boggie 5th gear......but there was lots of time to accelerate, but did it at the no so perfect , 5000rpm, well below peak HP. my guess is that they used a lower gear box to achieve the records.
peak hp for the holbet car is aroud 5700rpm, and at 5000rpm, HP levels are only about 82% of max. I estimate, round 240rwhp!!!!! so, its tough to think that they did it with the stock 2:2, but I guess its possible.

UpFixenDerPorsche

Give them time Ducman; Just give 'em time.

James Bailey

They had at least two transmissions at Bonneville one a 2:54, ran 7 inch wheels on all four corners, no exterior mirrors, and the brains were fitted with external chip holders for " quick chip changes" to no doubt bump the RPM.....and an extended under tray and also ran it lower than stock.....not to mention the 1986 camshafts that happened to be in the engine All to set a record for a stock production S-4.....yea right !!! some mention of a larger front stabilizer bar....
All of which is why I have always questioned how "stock" that original engine actually was......they went to Bonneville determined to set a record. Built an S-4 out of an 86 shell long BEFORE actual production ever began, did several small but obvious cheats to make it happen. And did extensive testing at Nardo in Italy to prove that it was fast enough and could survive....

mark kibort

i would think they ran that 2:54 to make the record, but who knows . al is no longer with us to tell! I dont think the bumping RPM was a concern. it was going to be a 5th gear run no matter what 5000rpm with the 2:2 was way down on hp at that point the 2.54 kicked it up just a tad (15%!!!) and that would have allowed 5700rpm, OR iin other words, MAX HP potential. there was no need for a rev limit change

I dont know why you question how stock it was.... alll of those things they changed were within the rules. (from what i heard) AND, just because they used a stock grind, 85 camshaft which became the GT cam, doesnt mean it was a cheater motor. heck, the cam was from the prior year !!
the engine internals were stock . it was truly the first S4 engine, #00004
not even a squirter block. stock bearings, stock crank, stock pistons and rods.. i showed you all the pictures of the disassembly. AND, it made no more hp than the same set up motor that Ron had with Mark. 320whp with headers.
it did have on it, some stock looking sway bar, that seemed to be porsche and it was larger than stock for sure. it survived ............for a long time too! i had 120race days on the car. LOVED that car!!! then, some idiot at the track, had to take it away from me. (us)....... very sad.
oh well

Imo000

I thought the GT cams are not the same grind as the early 32vs. Also, the engine configuration that you endex up with could easily be totally different than what they had for the land speed runs. I would not be surprised one bit if the engine looked like and S4 but it was bigger out to make a lot more power than the factory spec. Did Guinness check what the internals were?

heinrich

Imo, I have had 32V altered to GT and as I understand it they are identical grind/ angle ... etc

heinrich

Come on Brother. The 86/85 were basically S4 with a better intake

ptuomov

Same lobes, but S3 LSA is 114 and GT LSA is 110, I think.

dr bob

Mark--

Event notes say that they tried both gearboxes, and had exactly the same results. Kind of points to downforce and traction issues as the limiting factors on the salt. Tires slipped on the salt regardless of the gear ratios used to spin them.

This is a case where modern traction management would give you a percentage of slip, then start dialing back power as slip percentage went beyond the 8% or so considered max allowable (in my dark ages anyway).

Cosmo Kramer

Here is a quote from Jim Morton after some flow test on a stock S4 manifold

For those interested in another opinion on the OEM manifold, it is actually ahead of its time with the flappy resonance concept. For a street car the flappy / cross resonance idea likely adds noticable bottom end torque... a good thing. The issue is how the poor flow of the runners limit the size of the engine on the top end. For pure street use on a 5.0 or 5.4 engine, I am not sure I would throw out this manifold so quickly. As Sterling mentions, there are other areas of restriction to look at.

If drivability through out the RPM range is desired, the OEM manifold is likely better than any aftermarket venture, given what a good development effort costs.


So other then a pure track application where the revs are a the top of the range all the time there's no real need.

James Bailey

Correct Porsche designed a pretty good manifold for the purpose intended. Now start putting in modified cams, increasing displacement, proper exhaust , and spinning the RPM up or ALL of these and no surprise it comes up short.
The initial post about the Ferrari compared a stock car dyno to the modified intake being run with custom exhaust , aftermarket engine management so more fuel and ignition advance , and stock cams but advanced cam timing.... And had a big "improvement"...

Going to be fun to see Greg Brown's finished intake

Jim Morton

Wow, blast from the past by Cosmo...

To add some numbers to the discussion:

When working the stock S4 manifold, we found the manifold to be very unbalanced runner to runner. Many have seen this and discussed the issue. CFM values ranged from around 260CFM@25" to 285CFM@25" for the one best case runner.

After destroying one cast to investigate the flow challenges, we modelled possible porting using clay and testing on the flow bench. After several tests, we came up with a mod plan that got the worst runners to just over 280CFM@25". With this, we left the 288CFM runner pretty much alone. So, after a few thousand spent on flow testing / modeling, we had a port design for a S4 intake to have a range of flow at 280CFM@25" across all 8 runners.

Next up was trying tot solve a problem in the throttle body casting. When "flappy" was closed, the upflow out of the throttle body was not balanced by about 30CFM@25". Like the intake, we destroyed a throttle casting working to see how it might be modded for better balance. While doing this investigation, it brought up the question of where to place the throttle and how large the diameter. As I recall, for a 500HP/500 lb.-ft. torque engine plan (i.e. "square" force/power), the thotttle plate needed to be about 1/4" inch larger, but the need looked to be a fairly big project.

As many know, I looked at the overall value to continue with the costly development and elected to stop. I still think about these engines often and really admire those who keep up their well engineered developments.

Cheers !

mark kibort

yes, it will. but as we saw, there was some really nice gains..... big in my book, with the GT and an exhaust system with an un-optimized intake. HUGE hope that the GB intake will have substantial gains.

well, the revs at the top is where the HP is, and the s4 manifold ends up very short. this drivability thing, is great for traffic and being either lazy or not interested i using the right gear when you want acceleration. IF YOU DO, then the intake has to go and no one really cares about the flappy's purpose unless you are driving around town and dont care about maximizing hp and acceleration.

yes, and that's why it probably didnt matter what gear box , as slip was the biggest factor. your 8% number is close enough for street tires, probably a lot less for the salt and near 4% for race rubber. dont think that computer controlled traction control would have helped Holberts skilled foot. if you are slipping, there is not much you can do except be more precise

No, they are not the same lobs.... what gave you that idea? the GT and 85 cams have 10mm lift vs the S4 9mm lift

I allways thought that the old intake would perform better. i think it has a larger diameter throttle body. but , GB did tests and it didnt help when put on a S4 so i seem to remember him saying.... true?

if you are talking a S4 32valve, that would have to be a base cirlcle grind. angles are a little off but close vs the 32 valve from 1985-6. but the lift from the S3 is the same as the GT. thats why i was able to get near the HP when the Holbert cams broke (they were GT specs) by just modifying a set of 85 cams to fit the S4 engine heads

They were close to the same grind as the GT cams. the 85s were slightly different angles, but exact same lift. considering the dyno runs i did and how it matched the the GT that was modified the same way, AND the fact that there was report that the gear box didn't matter (meaning 2.2 running at 5000rpm vs 2.54 running at 5700rpm would produce near 30hp difference) shows that HP was not the issue, it was grip.
by the way.. i measured the engine dims when i pulled it.. it was stock. nothing was out of the ordinary. stroke, bore, crank , rods, pistons... all stock S4

Imo000

Doesn't matter what you measured if the engine was rebuilt to stock spec after the high speed record runs. As for the camshafts, as soon as you say "except" or "but" it's no longer the same. The only way to know the HP difference between the two cams is if they are run in the same engine, same conditions, same everything. Otherwise there are too many variables to know exactly what the HP difference is between the two.