Cylinder choices for 2L race engine
 

Hi guys - long story but please bear with me... , I have a 2L race engine which makes big power (~230hp) which is GOOD - but is basically undriveable for its intended purpose which is BAD - no power to 5900rpm then all hell breaks loose. Goes like a banshee to 8500rpm. The main problem is that it pops, farts and splutters its way to about 5800rpm unless you seriously get off the gas. We've spent a lot of dyno time with exhaust and carburetor tuning, but the problem is more fundamental. The goal is to get it driveable from 5000rpm even if it doesn't make a lot of low-down power.

81mm Biral cylinders
2.2+ heads welded and machined to fit the Biral cylinders
JE pistons machined for the above heads
40mm in port, 38mm ex port
Ti valves, colletts etc - AASE springs
Web 171/149 cams
46 PMOs
~11.5:1 - Twin plug - MSD
7R case, 930 oil pump, Pauters and so on...

Anyway, after mulling this over, I decided that the biggest worm in the can is the cams which I guess you could equate more or less equivalent to GE80. I discussed this with John Dougherty and he suggested his DC62 grind which has similar lift but quite a bit less duration. I have taken delivery of these.

I've just removed the cams and on further reflection, decided that the whole top end is 'too big' (particularly the port sizes) and that while changing the cams will help, the system is not in harmony so to speak.

Now, it just so happens that I also have a 2.7L engine which has beautifully ported heads with (if I recall correctly) 38mm in and 36mm ex ports. It also has a pair of perfectly matched 40mm Webers. Sooo - my plan now is to get these heads twin plugged, install the Ti valves etc and use them with the 40mm Webers on my 2L engine with the DC62 cams. Hopefully harmony will be restored and the world will get back into balance. And global warming will stop :D

The problem however, is that they won't fit on the Biral cylinders and I don't want to get them modified to do so. Which means changing the cylinders. Which raises my main question:

JB Racing has Aluminum Fin-Iron Sleeve Cylinders available and LN Engineering has their Nickies. My question is - does anyone have any opinions/views/experience as to which is better - or is it a coin toss? Any other input/alternatives on my plans welcome also...

BTW, my engine was built by a respected engine builder active on this board. It was built to my specification and any issues are entirely my responsibility.

Thanks for bearing with me.

The over porting problem can be remedied by a system we call Venti-Port.
The head /intake port is machined to accept a sleeve that is shaped like a venturi.
This new sleeve can reduce the port size and in some cases, as we have documented increase flow. The result is increased low end performance with little top end compromeise.
As for cylinders:
Nikasil 906 / 2.0 911 cylinders exclusively from Supertec.
We now have the first of our new 81mm 906 cylinders. Note the new sealing surface never offered before. It will allow you the put 2.2 heads on a 2.0 engine. Cast aluminum cylinder are less dense than other cylinders which means that the expansion rate is less adding to cylinder stability. The additional fins on the top edge of the cylinder add to cooling and cylinder stability not offered by an other cylinder manufacturer in over 35 years.
Reasonability price and ready for delivery.
Racing or street you won’t find any better.


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Thanks Henry, just what I need - more choices. Well, I did ask :)

The Venti-Port looks really neat. As a fix for the stated problem it looks ideal.

But to elaborate further, I intend to convert the 2.7L engine to 2.9 and the 'big' components from the 2L (PMOs, cams, heads) would, IMHO, be ideal in that configuration - not much has to be acquired except P&Cs and re-machining the heads.

Venti-Porting my existing big heads means I get to save the existing cylinders, but my other heads would then need serious work for the big engine and (which is where this whole re-think started), matching my 40mm inlet manifolds to the now Venti-ported heads (or placing the Venti-ports in the heads to align with the inlet manifolds) is probably not a trivial task :(

On balance, I suspect replacing the cylinders provides a better long term solution given I have two engines to deal with. Those 906 cylinders are looking pretty good...

Thanks for the help...

Your best bet for cylinders are Nickies...they cool SO well. Ideally, you would get new heads with optimized porting via computer modeling, then have the ports CNCed to match. Ideally, new Xtreme cylinder head castings would be used do you can machine and tune the entire intake tract from port to valve. You could also then custom contour your head dome for very flat pistons which help with flame propagation without losing CR. 2.2T heads a good second option, since they have a lot of metal to play with in the ports and have a decently shallow dome.

Not cheap, Nickies are $2K for cylinders and Xtreme heads can cost over $7K, but this is the ultimate option. If JE finally builds FSR pistons for a diameter smaller than 95mm, the entire combo would make any 911 motor as modern as anything on the planet with 2 valve induction.

Thanks Kenik.

That would be one fantastic solution and provides me with another option. Just one teensy weensy little problem - Her Indoors has her heart set on a new kitchen refurbishment in the near future which the (realistically ~$15K) cost of an Xtreme makeover might put in jeopardy. So my choices are:

a. Custom Xtreme heads, Nickies, more power than Hoover Dam - excruciating agony and death; or

b: Modified existing components, new cylinders, somewhat less power - continued, albeit precarious life.

I think I might go with b.:D:D:D

Thanks.

Definitely use Henry's cylinders...he takes the time to inspect the QSC cylinders and you will get an amazing cylinder. I would still get some 2.2T heads. then talk to Steve Weiner (steve@rennsportsystems.com) about head porting. He can do a port job as good as Xtreme on the heads for about $1400, so the net cost is much less than the option I described with 9/10 the benefit. I have his heads and they are amazing. You can see them here:
http://www.early911sregistry.org/forum/showthread.php?t=22220

Mark,

Why don't you have Charles at LN Engineering make a set of cylinders to fit your current JE's that will mate up with the 2.7 heads,..........

Its the best of both worlds without going broke doing this and part of maintaining domestic harmony.

Gentlemen, many thanks, The path is now clear.

Kenik, those ports look vaguely familiar - ;)

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I'll 'fess up - it was Mr. Weiner wot done it - but at my insistence.

Actually, it was only when I looked at my 40mm inlet manifolds on those heads did I realize just how radical those ports are and that the heads would be more appropriate on a larger engine.

I measured my other heads and discovered that in fact, the inlet ports are 36mm and the exhausts 38mm :confused: - go figure. Ancient Porsche 911 race cars seemed to go quite well with 38/38 so that looks like it'll be the go.

Steve, thanks for coming in here. JB, LN and Henry's jugs are all available with 2.2+ head registers so I don't think anything 'custom' is required? I'll have to run a mic over the pistons next weekend to ensure piston/bore clearances stack up, but considering it's done next to no work from new, I don't anticipate any issues there.

One advantage of Henry's jugs is that they look kosher which is one less thing to alert some jack-booted scrutineer - an 81mm bore is still questionable in the class I run, Anyway, I'll pm you re the heads.

Thanks to y'all for the input.

SNEAKY. :)

I am confused...which motor is the 2 liter? I thought you were building a 2.3L with the DC44 cams? I assume this is a different motor and one I vaguele remember reference to.

As far as the heads go, recall that the port diameter is less important than the aperture diameter behind the valve. Those heads are going to make better velocity than any plung cut head of the same port diameter. Did you run them on the the 2 liter or are simply guessing from previous experince they won't work?

BTW, that is a LOT of power for a 2 liter. I'd bet with a set of titanium valves you could get a cam in there that breathes as big as your current cams, but with much less overlap (meaning you would have much faster lobe ramps). Just another option...

Those heads are from my 2L engine as per the specs in my original post.

Precisely my conversion with John Dougherty - the DC62 cams have a tad more lift than the Web 171/149 but with less duration/overlap. My concern with 40mm inlet ports in a 2L engine is that they slow the inlet velocity too much. None of the early factory racers had ports this big! Given all the black scaley gunk on the back of the inlet valves after only 1500 miles, it's clear to me that the driveability problems are caused by serious reversion. A bit more inlet charge velocity from a smaller inlet tract and less overlap should get rid of most of the reversion issues.

I'm in the throes of composing an email to Steve as I write this.

Not getting the Aussies confused are you Kenik ;) ?

Not far away now.....

If you are getting that much reversion resulting in poor driveablity wouldn't make sense to look at the headers and exhaust ports? i would think that preventing or minimizing the exhaust pulse getting back into the cumbustion chamber would be better for driveability and not hurt the power you are getting from the cams/port sizes. would stepped headers or smaller exhaust ports relative to the header ID work? also would adjusting the cam timing help - i would think advancing the cams a little might shift the torque lower and the cam overlap would occur when the piston at point in the stroke where it is not sucking in so much exhaust. i'm really not sure if any of this would work but i'm curious what others think.

Ah hell, I guess I am. :)

You ask very good question grasshopper!

I spent two weeks on an engine dyno with this thing. Part of the time was spent experimenting with headers and mufflers. I had 1 1/2" and 1 5/8" headers and three different mufflers - all 2 in 2 out with internal crossovers. I chose the combination that gave the least reversion - interestingly the 1 5/8" headers with a muffler with the least back pressure. The dyno guy made a comment like 'This thing really wants to breath'. But it was obvious that there would be problems - I was hoping my close gearset would allow me not to fall into reversion territory, but it just ain't possible. We kicked around the idea of stepped headers, but the effort and costs involved vs the chances of coming up with something that might actually work simply made it impractical.

Exhaust systems are one of the least discussed issues on this board IMHO. For street engines that's not surprising - there are any number of good, off the shelf products available. But for competition or unique engines, it's surprising the issue is not discussed more often :confused:

Several observations. Firstly, for competition, it seems to be easier to build a good big motor than a good little one. Secondly, the basic parameters derived by Porsche 40+ years ago still hold - more or less - notwithstanding advances in cam profile thinking. Thirdly, exhaust systems seem to involve voodoo and witch doctors :D We are fortunate to have the active involvement of several witch doctors and it would be nice to get more insight into their exhaust voodoo :D

Some thoughts on this subject,.......:)

1) Its no more difficult to build a fast small race engine than a big one; the differences lie with their respective powerbands. All things being equal, a powerful small engine has a narrower effective power band than a bigger one along with drivability issues when at lower RPM.

2) Porsche's basic engineering isn't far off: we've learned how to improve their durability at higher RPM's and modern camshaft and cylinder head R&D affords the ability to make more power everywhere in the range.

3) No "magic" in exhaust systems,.......the results simply come from spending a LOT of dyno time trying many things to see what provides the best "area under the curve",..not just a big peak number thats only useful for bragging rights. :) :) Needless to say, this process is not inexpensive and the final products will reflect the expenditures.
This is not a "one-size-fits-all" proposition, small engines react differently than big ones and the final design must be tailored to the engine configuration as well as how the car will be used.

JMHO, of course,

Do the Supertec cylinders still need the cylinder head to be welded around its perimeter and are there pistons available?

What seals do these cylinders use? or do they use standard 2.0 litre gaskets.

No welding required, no gasket required. Henry has pistons too.