A.Wayne

I have and your guessing , the stock stuff is pretty good and well sorted out, the factory design optimizes TQ/hp over a wide curve. the turbo location gives you good CG for handling , now If you plan on reving to 8k and over 500 bhp then you will of course have to optimize.

Not much needs to be changed to get a 2.5 in the 400-500 bhp range, you can uprate header size and xover tube and of course boost pipes et al , but the design and location was well thought out , same for the stock intercooler and it's location, core is good too, especially when you dont vent the header panel best to duct the hood ....




Regards,

A.Wayne

The 951 is running the 924carrera gts/gtp setup , well a derivative of it , difficult for Weissach to compete with internet youngblood knowledge, you know the ones still struggling in 2013 to match the factory power of 30 yrs ago ..

Thom

Since we are several 3.0 folks who have noticed hitting a wall with the stock intake past 6k rpm, and I did back-to-back testing comparing the stock intake and another one with short runners that confirmed the issue with the stock intake, I would assume that the engines you have worked on were not properly-breathing up top? What levels of back pressure were you seeing?

I agree that the stock intake is a good piece... that was designed to work on a 2.5 engine. If I am to build a high-dollar 3.0 I won't want it to feel like a modern German turbo diesel engine... or single cam NA V8, if that talks more to you folks on the other side of the pond. I get the feeling that most car guys sateside put an emphasis on mid range performance because they are all baby-fed with national V8 spirit of performance, and as I much as I have tried to tune a 4 cyl this way I got brought to the cold hard fact that we can't have both a copious mid range and a screamy top end, unless perhaps if going crazy with VTG turbos, variable length intake, or other modern expensive tricks.

Also, if you have only worked with 2.5 engines I would understand that the issue may not be as easy to put into evidence.

Voith

I wonder if the 8v 3.0 engine porsche built had same manifold or did it had larger diameters.

Chris White

Please keep in mind that the 8v 3.0 turbo motor that Porsche built was built to complete in a power limited (and low power limit!) race series (ADAC GT). This comes up quite often where people like to think that the 8v 3.0 turbo was the 'ultimate' development of the turbo and use believe that Porsche knew better than turbo the 16v....in reality the power limit for the race series could be made by a 2.5 very easily (337 crank HP).

The stock manifold can support 337hp very easily, so I would be surprised if Porsche did anything more than port match the 2.5 manifold to the 2.7 head ports.

Chris White

It looks like you are mixing two issues here - resonate tuning and flow. Easy to test - if the power roll of gets worse with boost then is flow related. Since I have had 2.5 engines run to 7k on 'modest' boost with out a big drop in torque I can say that the stock intake does not 'hit a wall' with the resonance tuning.

Flow is a different matter - and when it comes to flow you are looking at a system including the turbo and exhaust manifolds, so the Wall Effect can be influenced by many things.

BTW - back pressure is, of course, not a function of the intake manifold. If the back pressure is going up a lot then you have turbo selection issues.

I can speak for the Yanks that know how to drive...the old saying 'torque wins races Horsepower sells engine' is still true. torque gets you out of the corners and that is where you make speed on the track. "area under the curve" is what matters.

"baby fed with national V8 spirit of performance"...hmmm....I'll put on my national pride hat for a moment (just for fun!)

Yanks also built the first V12 and V16 engines.

The V8s used in the NASCAR "stock car" series have higher piston speeds than Formula 1 engines - and the engines make almost 2 and half time the torque of an F1 engine and over 100hp more peak power....from a pushrod engine!

BTW - reading in to what you have posted makes me think that what you really want is a 16v head with matching intake. Then you can set the rest of the engine to happily run up to 8k rpm if wanted. You are fighting many issues trying to get an 8v to run well over 6k rpm. if you want to set up an 8v to run efficiently at 6500 and higher you need to also invest in a dry sump system to keep it all alive on the track. If you are going to that extent then swap the head. If you are not going to dry sump it then keep the RPMs down and tune for better mid rage torque.

Chris White

This is what you need to do to get some top end....

Dutch944

And again wise words from master White!

But the blank i see, what is it supposed to be in your last post?

Thom

They did not even open up the ports since the head is a modified 951 head that reuses the stock 951 intake. What they only did was to improve flow by reducing valve stem size from 9 to 7mm.

I think that swapping individual components on my engine, checking the logs and retuning accordingly after each mod allowed me to get a pretty good picture of how components balance out eachother. To suggest that I am mixing anything suggests you may not have paid atttention to the various remarks I have done in other threads...?

You missed my point, which is just that people stateside seem to be more sensitive to torque than HP and may mostly try to get the same engine behaviour from a turbocharged four as on a NA V8, which is, IMHO, not the most appropriate way to tune a 4 cyl.

I get your point about Nascar engines, but I'm yet to see one in a F1, where imperatives like efficiency are increasingly forced onto manufacturers. I suppose we won't even discuss fuel efficiency on Nascar engines?

The CW juke box seems to be blocked on the same record again
I think there is no "need" for 16V when using a suited intake, and that is not the stock intake. I suppose the curves at the first point of your thread here makes that point pretty well. Slap the stock intake on this very same engine and the curves will be "funny".

Chris White

fixed it.

Chris White

What you are mixing is the 'cause' of the problem that you are trying to fix - is it the resonate tuning or the flow limitations of the stock manifold that you have a problem with? Your post is mixing these together, at one point you seem to say its a RPM problem and then the next its a flow problem.

I don't read all the Rennlist posts...not enough time in the day to do that and actually get something accomplished!

I would rather emulate the torque curve of an electric motor...
My goal is to have as broad and flat a torque curve as possible. that it what you will get with a well engineered set of parts (turbo, cam, intake, exhaust and tuning). to put it bluntly any twit can make a couple of mods and twist an engine to a higher rpm and see a HP gain. HP is just an RPM factored torque measurement, you can modify and engine and make more hp and less torque. Not a very bright thing to do but its done everyday.

So, its got nothing to do with wanting to have a V8, its got to do with getting the best torque curve. If you like a 'dyno queen' curve (very peaky high rpm set up) that's fine for you....but its a crappy set up for real world performance.

4 cylinder or 8 cylinder - why would you goal be different? A broad torque power band it what you want.

Last I checked F1 didn't allow 5.8 liter engines .....and fuel efficiently is a big deal to NSACAR. In a 500 mile race one less pit stop is a huge advantage.

I like pretty much all forms of racing, each has its own technical barriers to over come. F1 was more interesting before RPM limits and design freezes. The DRS system is right out of the NASCAR theme - bunch up the cars when ever possible to make it interesting!

So - all that being said - what is the real goal with your engine? Race, DE, street, show or just tinkering around? I would answer things differently depending on the actual usage.

67King

It was mentioned briefly by Chris, but it is a point completely lost on most people. You can use a 16V head to get more torque than an 8V head, not just power. The spark plug is in the right place, so ceteris paribus, you can run, say, 9.0:1 instead of 8.0:1 on pump gas. You can also tune the intake (assuming you can package it, which is questionable) to hit at a lower RPM point, and be more detonation tolerant.

Those factors will also help you spool a bit more quickly, which does indeed help the car feel more like a V8 than a high strung fancy four. If you haven't done so, and get teh chance, go drive a newer DI turbocharged 4. My old Mazaspeed6 felt like it had a V8 in it, because I was at peak boost darn near off idle. My current driver is a 6 cylinder DI (BMW 535i), and it is much the same way. I actually checked out 550i's, too, but found the 6 with a Juicebox to be a much more drivable car.

Your point about the "baby fed V8" stuff with Chris responding about NASCAR sounded to be like it was chastising to a degree. Chris' only point, as I inferred it, was that there is more to their engineering than just "they ain't no replayce-minnt fur displayce-mint." I'll tell you first hand. America has the best engineers in the world. They just also happen to be the most held back by the financial organization of their employers. Ford could build a Ferrari tomorrow if it chose. Ferrari could never build a Ford. Power is a whole lot easier to do than affordability.

What the Americans could NOT do, though, is compete in F1. Why is that? Again, I can tell you first hand - the motorsports divisions fall under marketing, NOT engineering.

Chris White

And the fact that I don't think that anybody in the states could stomach sucking up to Bernie....

Thom

Ok, I don't think we want this thread to degenerate into a useless US vs ROW chest-beating contest.
We were discussing intakes, and I was just pointing out that the stock intake on a 3.0 8V was seriously strangling the engine up top. I'll keep it to that point.

Chris White

Nothing serious - I am just having fun with it!

To really discuss this we have to have a little more defined terms - 'Seriously' is hard to quantify, do you consider the dyno charts at the beginning of this thread as seriously strangled? is addition 'up top' needs a little more definition. As I mentioned earlier I would not advise running a 944 motor past 6400 on the track without a dry sump - so I limit the top end to 6400 for most engines.

All that being considered I would trade off a slow roll off past 6k rpm (20ftbs per 400 rpm) for an earlier torque result (100ftlbs per 400 rpm). using the 'area under the curve' evaluation you can see that the torque curve building up to full torque has a much steep slope than the top end gradual slope - so moving the curve to the left will actual gain more area under the curve - and a better real world response.