Steel lined cylinder observation

[DonE]

When I lost 3 cylinders to detonation on my turbo rebuild project 4 months ago, I looked for alternatives to the stock 3.2L cylinders that were bored to 98mm. All 3 cylinders were split top to bottom and one had a hole at the top. None of the pistons or heads were damaged in any way. The rings however, were in hundreds of pieces.

So, after a lot of research into Nikkies, iron lined cylinders and bored stock cylinders, I chose the iron. If you are somewhat in the same position, maybe this will help.

Here are my observations based on assembling the engine myself and about 4 weeks of tuning and running the car.

First, I got the cylinders from JB Racing in FL. They are iron sleeves with pressure fit aluminum fins, cut from billet aluminum. I had the spigots machined out to accept the larger liners - the fit was perfect: the head mates to the liner, the liner presses against the fins, and the fins sit on the case, thus giving deck height like stock. The deck height by the way was exactly as JB indicated on all cylinders.

By using iron cylinders, I didn't have to use the cast iron rings either. According to JE (where I got my custom 98mm, 8.0:1 CR pistons), they stated that their pistons are designed for iron sleeves, however they work with AL as well. Therefore, the fit of the JE with the JB cyinders was perfect and measuring deck height was consistent across all 6 cylinders. I'm also using custom chrome rings from JB ($250) that aren't as fragile as cast.

After assembly and start up, I drained the oil after about 70 miles. Both the engine mag plug and oil tank mag plug had minimal amounts of metal "sludge" - felt more like grease and barely covered the mag pick ups.

I've also noticed there is no longer the blue puff of smoke on start like the stock and re-bored 98mm gave me.

After 250 miles, there is still no smoke on start, there is no oil coating the intake from the crankcase oil breather and there has been no noticable oil comsuption. This seems to verify JB's claims of reducing blow-by compared to the stock thin-walled cylinders.

As for temp control, there is no difference in indicated oil temp and CLT temp on the TEC3r software compared to the stock AL cylinders. The ambient temps here in the ATL area are in the mid 80's and my oil temps range between 85 - 102 C (cruise and traffic temps).

I've had the car under full boost already and it seems to have the same power as prior to the engine failure. I'll confirm that this week at the dyno when I fine tune up top.

So, overall, I am completely satisfied with the fit, quality and performance of the iron sleeved cylinders. JB Racing did not ask me to say any of this and I didn't get paid. They have an excellent product you should consider if you ever need cylinders. Many thanks to Mike Bruns and everyone at JB for giving great advice and supplying an excellent product, on budget and on time.

[safe]

Isnīt there a drawback to using steel lined cylinders or did Porsche use nicasil just for fun?

[DonE]

Probably weight savings and it might have been a good match for the mahle pistons. Otherwise, I see dis-advantages going stock as mentioned above for my application - high hp.

[iamchappy]

Thanks for sharing, I too am looking into alternatives from the stock cylinders during my rebuild this gives me another option other than the Nikkies to look at.

[safe]

I'm skeptical.
Porsche went from biral to aluminum with the 2.7 because the material was to thin. How has JB racing solved that?
Also wouldnīt an all aluminum cylinder be better at conducting heat?

[DonE]

OK

JB, in my opinion, got around this by machining the spigots to accept the larger diameter steel cylinder. These are much thicker in the 98mm profile than the stock cylinders at 98mm. This makes the cylinders much stronger and resistant to warping (blow by)under power.

As for cooling, I can point out two things - JB uses them in race motors, mostly endurance, remainder sprint. They are very successful. Second, the increased number of fins they use (made from billet AL) to disburse heat is more than what is found on the stock 3.3L and 3.2L cylinders. This next point is my opinion completely, but since this blow by is now nil, oil in the crank case now stays in the crank case - cools and lubricates all parts better.

Rgds

[ANTONIO]

Don,
Nice input, I'm considering these myself for my next project,I'm going to try them on a 3.8 993TT running DTA injection, but to the point, how much boost are you using? Do you fear any issues with head lifting under boost? I guess the sealing on the head/cyl. area must be top notch. I will try this cyls. and post results later this year!.,cheers,Antonio.

[DonE]

I run at 1 bar around town and can safely run 1.2 bar with this set up. The pressure is not the problem - its heat. So, 1.2 is very limited. The sealing between the head, cylinder and case is as close to perfect as I can measure in my basement garage. Good luck.

[David]

Good info. I hope I don't have to put it use.

Man am I slow/lazy. You rebuilt your engine twice and installed EFI and I'm still not done.

[DonE]

Yep, but mine's not running right (actually not at all thanks to TEC3 ECU). Maybe you going about this smarter....

[YTNUKLR]

safe, the original Biral Porsche cylinder was basically a twice-cast piece; it has a cast IRON liner, then some aluminum fins are cast onto the liner. Not necessarily intending to plug JB (though they are good guys in my experience), they have built a cylinder with a STEEL liner, and the aluminum fins are compression fit with something like 11 tons of pressure. There is no separating or washboarding cylinders like that. And, I think the fins are forged and extra-large, rather than cast like the original Biral cylinders. Charles Navarro (of Nickies) posted that steel liners such as the JB Steel, can take something like 120-130K psi, whereas a Nickies takes a still-great 54k psi, and a stock Porsche cylinder takes maybe 20-30k psi. FYI.

[cnavarro]

I'm not sure if i'm reading it wrong, but i'll clarify otherwise. Since this seems to be a hot topic, I did some research. Back when we made "biral" cylinders, we used spun cast ductile liners (trade material MOLY 2000) which they quote on La Sleeve's website as being 48,000-53,000 psi yield strength (lower than I was actually expecting). I don't claim to know what liners JB uses and for all we know, they are using something even better, which is possibly the case. Regardless, that means the average ductile iron liner that is commonly used is right on par with the alloy we use for our cylinders, strength wise. It's at operating temperature where there is a difference, being that the ductile iron liners do remain stronger at temp BUT if you exceed the thermal capacity, no amount of strength will keep the liner from going south.

That said, your only limitation is how much heat you generate and how long a cylinder can stay dimensionally stable at that level. Case in point- cast iron 103s on the Porsche 914 have a lifespan of 5-10k miles, even at less than 50 HP per cylinder. Although they are physically more dimensionally stable than one of our aluminum cylinders at the same bore, they still fail by means of going out of round and not sealing at the cylinder head. We've also observed that the heads get pounded from the expansion and contraction differences. And that's all normally aspirated.

You just have to find the point where longevity vs. performance vs. cost is justified.

[Rob 930]

Chuck,

I'm very interested in what you have to say on this topic, and in your products, but unfortunately, I don't know what conclusions to draw from your post. And it leaves me with more questions than answers. Could you perhaps give a little more background or detail, and maybe conclusory remarks?

Here are some questions that come to mind: Is it your thought that the numbers quoted by the previous poster (YTNKULR) are incorrectly stated? What relevance does yield strength have on cylinder choice? Does the diminishing yield strength at operating temperatures suggest that ductile cast iron is superior to aluminum? Are cast iron cylinders more likely than aluminum to have their thermal capacity exceeded? To what degree is this important for Porsche applications? Bottom line: is there an inherent benefit or disbenefit to cast iron (under any set of conditions) that you can explain?

It would seem to me that if cast iron cylinders are stronger than aluminum, then if you have two cylinders of equal dimension, cast iron would be superior, except for the issue of weight. But I have no idea how other factors, like heat rejection play into the equation.

[cnavarro]

Diminishing yield strength at temperature of aluminum versus iron just means physically, at operating temperature, one will yield before the other (aluminum first). Yielding is as in complete failure, not what I would consider normal wear and tear. This is where a sleeved cylinder shines though- if you are really, really pushing the limits, running lots of boost, running hot, and doing so for short periods of time measured in hours or at most race seasons, the stength of the iron liner is what you need.

You also have to realize that by this same token, you are making lots of heat, more heat than what the cylinder can dissipate, so other components are exposed to greater temperature (and heat fatigue- as in heads with their seats, guides, valves). Again, in a race engine, longevity on the scale of what the oem intended is not a consideration. Porsche themselves phased out first cast iron cylinders and then biral cylinders for that same reason. No matter how many aluminum fins you cram on the outside of the cast/ductile iron liner, you still have two materials with significantly different rates of thermal dissipation. That's where I hoped the example from the Porsche 914 I cited would help explain the phenomenon i'm trying to describe. The factory aluminum cylinders have a thermal conductivity of 120 W/m-k. Nickies have a thermal conductivity of 240 W/m-k. Ductile Iron has a thermal conductivity of 36 W/m-k. It should be easy to understand why Porsche made the choices they did.

A great source for reading up on ductile iron is http://www.ductile.org/didata/Section3/3part2.htm. The figures I have for factory cylinders came from sending them out for material analysis. I used a 100mm 3.6 cylinder and a 97mm 3.3 cylinder, among others. To be thorough, I should also mention that I tested the factory cylinders for strength and the strongest yield I found was 32.5k psi as compared to the figures I quoted for Nickies and for ductile liners in my last post. The figures quoted by the previous poster about the strength of the liners may have been incorrectly stated by myself originally- unless JB could clarify for us, we'll just have to estimate theirs is at the high end of the spec at 53,000 psi.

[JeremyD]

I'll second a plug for JB Racing in Florida - and for those that don't know - they support the Alex Job ALMS team extensively. The guy that flame ringed my cylinders flew to Portland for the ALMS race in the middle of my job. Dave White racing uses JB Racing extensively for the high HP engines.

Professional, know their stuff, they will talk to you about plusses and minus of each choice.

[cnavarro]

Exactly, to be perfectly honest, I don't see myself as being in competition with JB. Nicely put Jeremy. They have a top notch product that most definately has it's place in race applications. I'd love to see our host selling it side by side with Nickies because there most definately is a need for both products. To accomodate for the levels of boost their cylinders take, i've had to make undersized cylinders to add additional wall thickness to provide the rigidity required for that level of boost.

[JeremyD]

And I'll second Charles and his nickies too another top quality product. If I could have swung the cost I would have nickies in my engine - maybe the next rebuild Charles...........

[Eagledriver]

It sounds like these JB cylinders are strong and of high quality. I don't understand what problem they are solving though. Don had his engine blow up due to detonation. Do these JB cylinders prevent detonation? Do they not become damaged when the pistons and rings fall apart due to detonation? Do they run cooler than nickasil?

Porsche found that there was less friction with Nickasil and more power. How do these steel lined cylinders compare in that area? In addition to that they seem to last forever (as long as they are not exposed to overheating or detonation.

It doesn't sound like there is much wrong with using these cylinders just don't see the advantage.

-Andy

[safe]

Charles: So if I got you, if you have a high boost race engine JB steel liners is the way to go and if you have a N/A engine Nickies (or maybe stock) would be better.

[cnavarro]

For a REAL turbo race engine, JB cylinders would be a no brainer unless dispacement can be sacrificed for wall thickness. Again, if comparing to stock cylinders, the JB cylinders are light years stronger, as Nickies are too. Even on street turbo engines Nickies work fine. Example in point is running a 92 or 93mm 930 cylinder. We haven't as or yet found a level of boost or accidental overboost that Nickies can't handle (which as of this date is 2 bar). Primarily Chris Carroll of Turbokraft, Inc (Pheonix, AZ) has used a few sets and seen what they can handle. CMW Motorsports also has been using Nickies for their customer builds for almost a year now with excellent results in their n/a and turbo race engines.

Andy, you're spot on. Nikasil does have lower friction. The figures I've seen from improvements on V8 blocks is about 8-10hp. I don't have a comparable figure from 911s, but do have figures from 356/912, 914s, and type 1s from builds done over the past few years and we saw an overall 15% increase in HP/torque and a 100-150F drop in head temperatures under a full load when going from cast iron or biral to aluminum/nikasil. Not all of that can be attributed to just nikasil, but also to the reduction of head temps (and cylinder temps) and a cooler, denser intake charge (n/a engines in all cases).

It would be interesting for someone to take a small 911, say a 2.2t and do a build with cast iron cylinders and dyno it. Then swap cylinders to birals then again to aluminum/nikasil. No other changes would be allowed to keep the figures comparable. This is the same process we used on the 356/912, 914, and type 1s in testing Nickies.

No cylinder can prevent detonation. All you can do is try to keep things cool, and that helps a ton, assuming many conditions including the tune of the engine and other factors. Accidental overboost will do the same thing to the pistons and rings regardless of cylinder choice. It is concievable that under those conditions where severe detonation and overboost along with inadequate fuel delivery, too much advance, etc. could cause the cylinders to split. The JB cylinder will hold up under those conditions far better than a stock cylinder that would most definately split. I've had customers overboost and detonate and the engine had to come apart. One cylinder had to be replaced as there was a hole the size of a quarter in the head at the sealing surface that intersected the cylinder (not flame ringed). Another single cylinder had to be welded to fill in a gouge (caused by the pistons/rings) and then replated. Neither case were in whole caused by overboost or normal operation. In both cases there was too much advance and in one case, bad race gas and in the other, the customer didn't think he needed race gas to run more boost and more advance :-)