Bill

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">To spin the 951 motor at 7000rpms (and above) you need to have a strong bottom end </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">TonyG,

I don't believe that the cam/balance shaft belt system that we have in our 944's were ment for high rpm's.

A strong bottem end is an absolute must, but the ENTIRE valve system must also keep up.

High rpm engines typically have solid lifters and stiffer valve springs. Stiffer springs are required to keep the valves following the cam at high rpms. Too stiff of valve springs and you kill the belts. Not stiff enough and the valves float.

TonyG

Bill

I would have to disagree.

Cam lobes riding directly on the valve lifter are designed for rpms. When you have push rods, rocker arms, etc.. you have a lot more valvetrain to move to actuate the valves (and a lot more weight to move around), and by default have a limiting factor.

Our 8V heads, are about as light and direct as can be. The only issue here is that we use a hydraulic lifter. It's takes spring pressure to keep the hydraulic lifters from pumping up.

Stiff spring pressure won't do anything to the belt. What it will do is to pound the valve seats pretty good if you go too stiff.

I'm stiffer than stock, but not that much stiffer because I use all lightweight valve train components. The lighter the valve train components, the less stiff your valve springs have to be for any given rpm (all other things being equal).

Now with respect to the balance shaft setup that's spining at 2x the engine speed. You might be correct. I've never seen a problem though.

FYI... I don't run balance shafts!

TonyG

fast951

So what turbo is included with your kit?

Once a kit is sold, the cat will be out of the bag anyway (at least with someone willing to take photos of the turbo and email them to Turbonetics, Innovative Turbo, etc... who should pretty easily be able to tell what exactly the turbo it).

I'm asking because I suspect my 60-1HiFi compressor is too small for my applcation.

I had intended to wait until I dumped the stock intercooler and intake manifold to work on the compressor further though.

Come on come on.... spill the beans.

Skip Wolfe

86944turbo,

What sort of hp are you getting at 20 psi? At 14.7 psi?

86944turbo

Skip,

The motor (on an engine dyno) showed a little over 540 h/p @ 6.4-6.6K, I do not have the sheet in front of me. The 500+ ft/lbs. of torque were realized at 5k. Two Bosch fuel pumps are used each capapble of 600 h/p. But with the fuel rich requirements of a turbo motor and the fact that the intake temps. on the dyno are, at times far above what I've seen and that fuel pressure was dropping after 5k, a second Bosch Motorsports .044 was added. The dyno pull was at 1.25 bar. A few other things.
The intake valves are 51mm ex. 42mm (w/nickel-vac face). Guides are aluminum bronze. Retainers titanium. Keepers steel. Seats are of Berrylium and (copper or bronze). The lifters are stock units w/oil inlets revised for the higher lift cam. The cast billet Cam has approx. .533 intake lift w/.502 ex. The pistons (I'd love to have Mahle, they do not make special batches) are JE, w/sealed power rings. Carillo rods. JE pro-pins. Intake is one of the Milledge barrell valve units w/individual throttle bodies. Tial wastegate. Combustion chamber, valves and ex. coated w/ceramic. Pistons coated w/gold ceramic. Sleeves are the ones from Portugal (Spun nodual iron). Probably the same ones Norwood used. 3 1/2" exhaust. Pressure plate is a KEP 2800 lb clamping force unit. As I'm sure you're aware clamping force can be deceptive in that it must clamp at the position where it's needed. 3rd clutch (Diabolical 6 puck solid unit). The 935 p/p I had was tested at slightly less. Since Porsche's 5 spd. typically breaks after 450 h/p, it uses a 968 6 spd. w/torsen (When I went through the 1/4 mile, shifted 4 times.) Intake fabrication is from Comptech Eng. Radiator (frame required notching) Ron Davis racing. MoTeC M4-Pro w/data logging, Accusump, Water spray bar for intcooler. Air/oil separator. Oil/water heat exchanger. 83lb./hr. inj. @ 3bar F/P. On boost 5+ bar is run. Big fuel line. TPS replaced twice. Now using same as Jaguar F-1. Expensive piece. Head (in box) was designed for 2.7. Appartently flow sig. better than 2.5. Then comb. re.comfigured as well as ports then heat treated. Concentric O-rings. The cost/genius waas in the R&D that lead to the machining not mentioned. Actual part cost is probably comparable to any other builder. I'll explain later why the detail. Race engine builders don't angle cut valves. Old school. O.K, so @ 18 1/2 lbs. 540~ h/p. 1 bar 14.7, sorry no engine dyno pulls, just specualtion. Maybe 460-490?

Skip Wolfe

86944turbo,

Outstanding motor! Did you have the motor built for street, track or dual purpose use? How long have you had the engine and has it proven to be reliable. I think one of the big questions on this thread is the reliablility of the built high hp motors. Milledge definitly has a terrific reputation for building top notch motors, and looking at your build write-up it seems like there weren't any corners cut. Just curious how much ongoing tinkering, modifying, etc is needed to keep things running without a grenade incident.

Maybe I can sell a kidney and get myself one of those.

86944turbo

I got a call one morning from Jon. He asked if I was sitting down. He told me that another customer was using the same ex. valves & had one break. Again, I think mine is the only street appl. of his motors. He suggested to replace them. I sent hime the head. The diff. was that mine were ceramic coated. Mine were in perfect condition. But ex. were replaced as precaution. On his own dime, he installed new valves, flew out and replaced head. Switched cams sometime back, made a run, e-mailed run to Jon, e-mailed new one back, easy download. The only problem was, clutches, now seems to be solved (Centerforce assured me they have nothing to hanlde the power). The TPS broke, new one fine. No tinkering. Just gotta pay attention to the MoTeC dumps. While trying to learn Willow Springs I asked an experienced POC driver to show me the lines, apexes, etc. He came out telling me this car has no business on the street. Jon says the same. I'm guessing 10-12k miles on it. While I do not baby it, I will not use boost until all temps. are adequate. Still scary.

86944turbo

While I'm in the mood, something I've gotta say. Some of these H/P figures quoted are, in my humble opinion, ridiculous. While it is not my intention to pick on any tuner in particular. It is going to be inevitable. The 446 h/p from the 2.5 w/stock bottom end is far above what I've ever seen or heard of from a builder. The RWD chart shows peak H/P before 6000 rpm. Is that correct? What type of cam, head work, etc. was in place? MAF for this kinda power? Yes, H/P #'s are important. I've seen reputable tuners profess that Porsche's tt (400 factory h/p), had in fact 480 h/p. It doesn't. It has 400 h/p. Look at the mags. test. 114 mph at the end of a 1/4. Calculate the weight, 3350-3450 and you get 400 h/p. Viper rated @ 450-460, you get 118-120 mph. Similar weight, more power. Look at M/T for their 1 mile accel., Z0-6 at virtally the same time/speed as tt. Why? Same H/P. I realize that the 1/4 mile is possibly the lowest form of motorsports. The speed at the end, does reveal h/p, probably better than any other form, widely used. Tire slippage, etc. really have little bearing on trap speed. Even w/drag slicks, speed (w/same driver, track, conditions, etc.) changes very little. Why do I think that this is a better barometer than a rear wheel dyno? My 434 h/p motor once dyno'd @ 467 RWH. They all have varying
results. Then one can say, "If we all use the same dyno". At the end of the day we want performance, not just a number. And, they can be manipulated. Did I say that. Also, we may never meet each other and find out. Yes, I'd prefer a mile run, but I'm trying to be realistic and practicle. A 951 w/446 h/p at the rear, should have 490-495 at the crank. I don't think Porsche's lose, but 9-10% through their drivetrains. Assuming vehicle weight is approx. 3000 lbs., it should hit 125mph, or darn close in the 1/4 mile. Hey, if I'm wrong on the 9-10%, the speed s/b higher. No G-Tech runs, please. All major tuners do this. Be it Hennessey, Lingenfelter, RUF, Saleen, etc. Not all are pleased w/results. But, it is an accurate comparrison of H/P.

m42racer

I have a couple of questions for Tony G.

When you say you are using lighter Valve Train parts, just what are you meaning? Valves, Retainers?

I don't understand something or possibly missed something here.

If you ARE running a lighter Valve and Retainer, why did you go stiffer on the spring? All things been equal. If you are running 'Ti" Valves and retainers are you using a Cam designed for these parts? If you are not, then you have failed to gain anything. If you are accelerating the Ti Valve as slow as you have to for a Steel Valve, then what have you gained. Accordinly, if you are deaccelerating the Ti valve as fast as you are for a Steel Valve, you are most probably going to hurt something. If this is the case, your engine ASSEMBLER, has got it wrong.

The RPM limit of an engine with respect to the Valve train is a factor of the design, weight of the components and the force required from the springs to keep things attached. Your statement regarding our use of hydraulic Followers verses rockers is somewhat misleading. You can use way more spring force, Valve acceration, RPM's etc, with a Pushrod engine using soild lifters , rocker arms, than you can with an OHC on hydraulic followers.

On tests that have been done, using the exact same Cam profiles, but changing the cam design allowing the use of solid Followers, approx., 12% increase in performance was achieved.

Most engine builders today use computer programs giving information about the Harmonics created into the ValveTrain and other forces etc., when different combinations are installed into the design. They look at these before any manufacturing, or assembly is done. I have read here about some ideas that most engine builders still use experience and the seat of the pants method. Well, not the engine engineer's I have come into contact with. They are very scientific, mathmatical and have a completly different approach. When all these factors have been taken into account, all risks accessed, engines are built and dyno tested.

One of the biggests HP robbers in an engine is the Harmonics that are created into the Valve Train by the Camshaft. Most Camshafts that we can buy have absolutely horrible Harmonics. The difference between their cam designs and a design done by an engineer is huge. I know of 2 companies in Ca., who make a alot of cams for Porsche's. Neither know what they are doing. One uses very old designs which were originally done way back by a person by the name of Whitman, I think that was his name. The other copies, badly, stock profiles and moves the centers around. Most of the stock profiles are of production design, not considering, as they don't have to, performance etc.

This is exactly why I want better parts for us. I am not trying to save anybody or anything. If parts are made for the 951, then make them properly. Most of the parts made for 951 engines were never designed with any engineering included. I ask the question. If its thought that this level is not important, then would you fly on a plane designed by your Tuner. If I had to pick which plane I had to fly on, I certainly would pick one that had some engineering thought put into it. Why should our aftermarket parts be any different. The cost will be the same. Maybe in some cases the cost will be higher, but then quality dictates cost.

I've read posts by Huntley regarding new cam drive designs etc. GIVE ME A BREAK! The old saying apply's here. When you can engineer yourself out from a wet paper bag, go on to the next level. I have been to his shop, and apart from a drill press,welder, and an old chassis dyno, and lots of high school kids running around, whats offered. The same goes for alot of these places. How many 951 Tuners do their own machine work in house. How do they control quality? Do they use production machine shops that rebuild parts for taxi's? If we are always comparing dyno HP's etc, then why are we not considering how to get real HP, other than slapping on some Turbo some guy said would work. Really good engines start with really good machine work. Then really good assembly, using really good parts. In most cases, all of the loose bolts, compliants etc I read about would not have happened if the same level was included.

Enough of this dibble, I've stated my opinion.

Lastly, 86944 Turbo has an engine that is of the quality I'm discussing here, it appears. The dyno results speak volumes. Of all the numbers I have read here lately, I know that they are real, crediable and what we all want. No excuses. No, that run was with an old Turbo, run # whatever was the wrong A/F etc. If your going to post numbers don't post excuses with them.

m42racer

86944turbo,

BTW, Mahle do make special batches of Pistons. 1 if you need it.I have some in my engine. Mahle have a small prototype shop very close to the main factory near Stutgart. The real engine builders know this, and have them made there.

TonyG

m42racer

Yes I'm talking about valves, and retainers (and more).

With respect to my statement about all things being equal. I think you know exactly what I'm talking about.

Just because you run lighter valvetrain components, doesn't mean that you still don't have to go stiffer on your valve springs. This is engine building 101 stuff here.

What I said (or at least meant to say), was that if you use lighter valvetrain components in car X than you do in car Y then car X will have a higher rpm limit with respect to valve float than car Y. This doesn't mean that car X will have the proper valve train to run at a specific rpm simply due to valvetrain weight. It sometimes means that you still need more valve spring.

Given the above statement, this translates into exactly what I said before. Lighter valvetrain will require less valve spring pressure to run at a specified rpm.. all other things being equal (like cam lobe ramps profiles, cam lobe heights, etc, valvetrain harmonics, etc...).

It's a blanket statement, but true nonetheless.

With respect to hydrauic vs solid lifters... So? Nobody ever said that a hydraulic performed better than a solid lifter? If you want to really dig into it, then you should use mechanical roller lifters into your argument which would allow a much better cam profile than either the solid or the hydraulic.

As far as the cam that I'm using goes... Talk to John Milledge. It's his cam, and he designs his own cams. Maybe you should write him a letter explaining valvetrain theory to him.

With respect statements that Huntley might have made.... What does that have to do with me? Huntley didn't do my head or valvetrain.

Landjet

Maybe sometime in the near future we could arrange a 944/951 convention in the midwest where you all could come from east coast, west coast, north and south meat in the middle, bring in the tuners interested and have one big get together and see what is what first hand. You can't get much more in the middle of the US than here in Wichita, KS and I would be willing to help set things up with the local Porsche Clubs. This would give everyone a chance to hammer out the good ,bad and BS and get a bunch of Great cars and people together. We could bring in a Dyno so everyone could pull on equal ground. Everyone could put there money,pride,truth and HP for all to see. Just a thought.

m42racer

Tony G,

Then say what you mean at the beginning.

BTW, you are not running a cam designed by Milledge. You are in fact running a cam sold to you by Milledge, who in turn paid to have it designed. I have no need to write to him explaining Valve Train theory, as the person who designs his cams is a very good friend of mine, so I'll keep any cam theories etc limited to those who know. No offense meant toward Mr. Milledge. Just stating facts to make my point. Don't believe me, ask him.

m42racer

Tony G,

BTW, just what do you mean by "(and more)"

Please explain.

TonyG

m42racer

Then Mr. Milledge would be a flat out liar.

He has told me directly (over the phone) that he does in fact design his own cams personally.

The "and more" reflects certain additional work/parts that have been done to the head/valvetrain (which initially was provided to my by Milledge).

What that more is I can't specify (or rather I won't specify). At least not yet.