tv

What could Porsche create today for 5 liter V8 in a class leading GT?


this is what has been done;

Audi R8............4.2 lt....430bhp @ 7800
BMW M3...........4.0 lt...... 414bhp @ 8300
F 430...............4.3 lt.....483bhp @ 8500
F458................4.5lt......570bhp@9000
BMW M6..........5.0lt.......507bhp@7750
Audi R8GT........5.2lt.......560bhp@8000
CarreraGT.........5.7lt.......610bhp@8000
F599gto............6.0lt.....670bhp@8250
Lambo aventador.. 6.5lt...700bhp@8250
Aston One-77........7.3lt...750bhp
Cadillac XV12.........7.5lt...750bhp
and
918 spyder...........3.4lt......500bhp@9000


Porsche does know everything these guy's know including being related to Lambo and Audi now. Their work on the upcoming 918 shows they can produce incredible power per liter in a V8. A new 5.0 liter should produce around 550, but why stop there, if it were to stay the way it had been in the 80's a new 928 would produce around 600bhp from a 5.5lt engine.

John Speake

This is current state of the art 5 litre V8 from Porsche, for a good compromise between low down torque and top end HP:-

Panamera GTS 4.8 litre V8 430 PS (316 kW; 424 bhp) @ 6,700 520 N·m (384 ft·lbf) @ 3,500-5,000

tv

The current V8's from Porsche are workman engines pushing around big vehicles - Cayenne and Panamera. Not exactly state of the art. For a new 928, and I keep hearing different things about whether one might happen, if it does I would expect a compromise between the 918 capability and the panamera. Much more like the Ferrari Italia spec

mark kibort

Its always HP. torque is just to micro of a measure.

Yep, i agree and a variation of what anderson has should be the goal for anyone experiementing with getting big power gains on the 5 liter

too small , too many curves and still too restriictive. we got the textbook, 290rwhp out of the 5 liter in most all itterations, but using the AFM. i cant imagine it is worth more than 10-20hp opening it up. and we even had a pretty nice lobie cam from devek. (b1). the S4 just has more to start with in the heads upward.

agreed

FredR

With respect, if it was that easy surely it would have been done already?

This thread is not about looking backwards, it is about looking ahead- removing any blinkers that may be present and that takes lateral vision.


Regards

Fred

IcemanG17

There have been plenty of stock internal S4 engines with only pure race exhausts that get 300whp pretty easy.......some GT's with near race exhaust have gone far over that....several near 330whp.....

It would be interesting to see an "andy clone" engine on a 5.0L bottom end... Since Andy's engine made about 608HP on the engine dyno or 95hp/L its reasonable the 5.0L could match that...or 475hp....say 400hp to the ground.....BUT that comes at a serious cost.....

Dennis's engine made 387whp or say 375whp taking out the wiggle......it did that with a full race exhaust Morton's cams and proper tuning.....

With stock S4 heads flowing near 270CFM at reasonable lift....they can support over 500hp.....Most chebby LS heads flow almost the same....LS2-3-6 heads flow 280cfm stock and those engine are 400-436hp bone stock with cat's...... They are between 66-72hp/L bone stock with cats....all can be much higher when properly built

Hilton

Note they all spin faster than a 928.. greater rpm's gives very "cheap" power if the engine's built for it.

From memory, Dennis' engine was also rebuilt very carefully - exacting balancing of the rotating assembly, lighter valve train, careful selection of bearings and rings for tolerances etc. to maximise performance and support spinning to higher rpm's.

The only "stock" factory engines likely to have that attention to detail are the clubsport engines found in the Clubsports and 928SE's.

Of course, Dennis' engine didn't have a custom intake on it - which would allow for significant improvements. I do think 380rwhp should be attainable (450 crank) with the cams/headers/intake combo and appropriate tuning - although it may come at the expense of low and mid-range grunt. The other issue that then brings up is oil packing into the heads - if you move the curve to support higher top-end power, then more time at high rpm's becomes likely, and the need for oil suction out of the heads increases (like Andy's stroker engine has after Greg B's development).

So.. enough of this ruminating.. who's going to do the headers/cams/intake work on a stock engine whilst keeping the heads on? Colin, can't you get Terry to do the intake next after his MSDS headers and X?

More useful info in this thread - sounds like cams and good exhaust should hit 350-375 rwhp, without intake modifications.

https://rennlist.com/forums/928-foru...s-alive-3.html

928mac

If I get a chance this summer ILL take it into the city for a dyno pull.

89 euro, GT heads, my intake dose not have the 4R just the R so I think it is just a stock S4 intake.
http://forums.928oc.org/vbulletin/at...8&d=1299726773

I removed the cats and installed a electromotive engine managment system.
I would like to install some cams but iLL see what is out there when I get the cash as I would like a lot of cam, but will see.

I think 400-450 at the wheels without boost would be max and more then I want to spend when the power adders can be found for less then internals.

Compression is also the key when you dont want to go blown, but pistons and rings are not cheep either and are a major build. Might as well do rods and have everything balanced if you go that way. IMHO

Jon B.

Don't forget about the early 32v. They make excellent power as well. We already know Ken makes good power with his S3, and I'm looking to add a set of Colin's cams as well as Devek Lv2 headers to my car in the upcoming year in addition to Ken's chipset.

Though I'm wondering what I may be limited to with my ecu...

Dennis K

Agreed. If the goal is 500 bhp out of 5.0L, the S4 intake manifold may still work. Jim Morton posted some great info here:
https://rennlist.com/forums/5558133-post38.html

The S4 manifold can be modified to flow better than the stock S4 heads. In turn, the heads can be modified to match the new capabilities of the modified intake. With the right cam and tuning, who knows where you would end up? Once you've done all this, you might find bottlenecks elsewhere.

If you want to play at Simard or Ott levels, then yes, ITB's are needed. For the relatively modest needs of a 5.0L, I think there's still life in the old magnesium girl.

Jim Morton

As relates to this thread and given that my name has been dropped several times, let me work to contribute to this topic without adding further slippery slopes or endorsement of any particular products.

With regards to a 5.0 liter engine, I believe that the question is how much power can be expected from the given displacement given how the engine is able to control the air flow through it and how high a RPM the engine can operate and sustain its life. Different engine designs typically have know compromises based on various considerations such as cost, physical dimensions and intended vehicle application. Avoiding the topic of "that which shall not be named", I think we must acknowledge that a 5.0 engine being designed for a 4X4 truck might not have the same design HP as an engine destined for a sports/race car. If we agree to this and move ahead with how much power is possible, then I feel that many of the questions become simpler. Here goes...

In my opinion, to pose a power question about a given engine displacement, you must consider the air flow needed to produce the needed horsepower, along with what fuel is being considered. With these estimated / known, then comes the question of engine efficiency and RPM. From my knowledge quest on 928 32V engines, here some interesting tidbits:

1.) As mentioned in the post Dennis referenced, I worked with a well know cylinder head resource and given initial observations of the 928 32V engines, we elected to re-work a set of heads seeking best air flow. Without huge expense, we were able to achieve 340 CFM at 0.425" of lift for the intake port at 25" of vacuum on the flow bench. This was the intake port with a basic bellmount at the opening. With the intake manifold on, the CFM through the intake port was reduced to 275-290 CFM, depending on which runner was used. Obviously, the in-balance between the runners was unacceptable to proceed with the stock intake. So these "max" heads have been on the shelf, while other options have been explored. All of the need is based in my needing/wanting a SMOG legal "hot rod" over building a race engine. It is also worth noting that all the flow result was not simply working in the ports of the castings.

2.) Going back to review the OEM airflow setup, we then worked an OEM intake manifold to seek best balanced flow as opposed to max. flow. After some welding and porting, the OEM intake was able to flow 285-288 CFM, again at 25 inches. With this established, next was to see what was needed to mate the S4/GT/GTS heads to the ported intake and still maintain flow.

3.) Based on flow bench work, at some point around the flow needed for 450+ HP (normally aspirated), the throttle body casting develops problems keeping flow to the driver's side uplift. The relationship of the casting radius, throttle plate diameter and angle begin to work against each other for each uplift port into the upper manifold plenums.

4.) After flowing a stock head, achieving 285 CFM, each port, is not that hard. There are many ways to do it and each way has advantage and comprimise, so I leave that detail discussion for each reader/owner and their chosen engine "guru". The "gurus" can delve into that topic(s) as they see fit.

5.) As I approach it, the next design challenge for the 928 32V engine development is how to apply the estimated / known CFM to establishing a working valve event timing(s) that best meets the objective of your desired power curve, one such curve result being max power. Mass and lifter diameter play a huge role in cam design / selection. Here again, different builders have different methods.

6.) In my opinion, max HP is most easily achieved by extending the torque curve into higher RPM without losing efficiency. How to do this takes considerable experience and understanding how combustion works for the choice of fuel and how that relates to efficiency. Again, each "guru" has their opinions. For me, the challenge and fun is to observe and build off how different guru apply theory to get tried and proved results. Again, this is "guru" territory with many Internet "engineers" chiming in.

7.) As FWIW, I approached tuning Dennis' engine not with a comparative 928 result in mind, but instead choosing to work off the mindset for what the well tuned 5.0 engine with it's flow potential, displacement and timing should be able to achieve. Each tuning move applied to Dennis' engine was not by someone else's recipe and done on the spot at the dyno. Test runs were made, data analyzed and tuning moves were applied and tested. Not all tuning moves worked. Although there have been many posted opinions about Dennis' engine with even some claims of falsified results, know that I feel that the engine is still not optimal and should be able to produce even more power, something along the lines of what I see from my 5.0 liter E39 M5, at least for max. HP... again not shifting the discussion to the "force that shall not be named" and how variable valve event timing helps that "other" curve.

8.) Overall, I see the tuning challenge for a given engine is to consider where the power is being bled off and learning to give the engine what it wants at those points along to curve, both fuel and ignition to better extend the "curve, not to be named" into the higher RPM. I feel doing this gives you "easy" HP.

9.) As much as I enjoy working on the 928 32V engine, there are other factors that make 928 32V engine developments rediculously expensive. Besides the cost of the bearings, gaskets, seals and core engine castings, the 4 valve / 4 camshaft design adds further costs beyond what many of the 928-ers consider. Add in the lack of a value oriented camshaft blank, like a CWC brand cam blank, all of these cost elements make further 928 development past basic tuning mods, VERY expensive. With the high variation / revision cost in mind, it's been a struggle to justify the expense to move forward with further 928 32V development.

10.) At some point soon, I hope that Dennis and I can hook up and test / tune / test his current (likely final) 5.0 engine assembly. Since the post of several years ago, there have been untested, further intake improvements. There are even more development ideas on the table, such as a new 32V cam profile and possible low cost windage improvement. However with each of these revision costs as high as they are, I doubt that neither Dennis or I will chose to afford the next step(s).

OK.... Hopefully this post is useful and on topic to this thread.

Regards

John Speake

Thanks Jim for that very interesting information. It certainly shows the way to extend the rpm range upwards in the search for more power.

In answer to the OP question, is this the path that Porsche would take today with a new 5 litre V8 ? I think for a car like the 928 they would go the Panamera GTS route.

FredR

Jim, Dennis,

Many thanks for sharing your fascinating insights and you have my deepest respect for your achievements. If we measure success in terms of bhp/litre you must be right up there and as I stated earlier that you did not lose anything I could notice lower down makes it all the more credible. You certainly appear to hold the 5L Blue Ribbon.

Part of the reason I raised this thread was out of frustration that I am running out of things that I can do without going totally radical. I do not think that shelling out $2k fora s/h set of GT cams on its own is worth the investment. Similarly I do not fancy gutting my S4 motor to fit a GTS crank/rods just to get back to a GTS motor for my GTS chassis and have a motor that still cannot breath.


When I visted John in the UK this time last year he told me about his project to eliminate the MAF and if I understand the situation correctly, how it opens up certain vistas that previously were not available to cam tuners.

Our experts seem to agree that the strokers appear to run out of steam with the stock inlet manifold but
Jim's comments clearly suggest there is quite a bit more it can do for a 5L that the stock set up cannot handle.

I picked up on Jim's comment about the throttle body being restrictive at certain flow levels- something I have wondered about for a while. This made me wonder what might be done with the stock manifold.

If the inlet tract were modified to two throttle bodies mounted on the inboard side of the radiator line and we dump the existing throttle body, would this help the motor breath significantly better assuming an optimal cam grind taking full advantage of the possibilities that John's new sytem offers ? Air filter mounted Mike Frye style.

Expanding on that concept, would modified plenum covers, made in CF[or metal] with an auxiliary air inlet port tee'd off the main inlet pipe [downstream of the main throttle] with an on/off throttle plate of some kind help the motor breath significantly better at full throttle? Appreciate we do not want to destroy harmonics of the plenum but at full throttle conditions one wants to remove any unecessary flow obstructions.

So, could an alternate flow path for top end performance liven things up?

Presumably if one has the hardware to facilitate more flow [cam profiles, exhaust system etc] could something "sensibly designed" along these lines have something to offer at relatively modest cost?

Just trying to encourage lateral thinking here- any thoughts on whether this type of approach could be made to work?

It would look very close to stock at first glance and retain the flappy. Carbon fibre always looks cool.

Regards

Fred

dprantl

Eliminate the MAF, install a larger single throttle body at the front of the intake, lower the radiator and have an airbox/filter(s) in front of the radiator. The air will have almost a straight shot into the intake. All those crazy bends the air has to take with the stock arrangement IMO is hurting the engine's ability to breathe. Something like this:



It won't look close to stock though.

Dan
'91 928GT S/C 475hp/460lb.ft

Randy V

That's where gut feeling parts ways with actual physics.

Air intake is not a bottleneck, despite the twists and turns you perceive to be slowing air delivery.