Sierra Sierra's marketing/hype man, John Naderi, posted these pictures from a Buttonwillow test day on Sierra Sierra's Facebook page last month. BTW John took all the pictures below and I simply stole them. You gotta love the digital age. Anyhow, below is my far more detailed version of the Buttonwillow test day and the events that led up to the T04 turbo failure. The BorgWarner news is toward the bottom, but in summary, BW's going to save the day (hopefully) with their new line of EFR turbochargers.

For past posts on the Sierra Sierra EVO 8, CLICK HERE!

The last time I went to a test at Buttonwillow with the Sierra Sierra boys was about a month ago (September). We had one of our typical problem laden tests. No matter how much preparation is put into the EVO, almost always something goes wrong. There are so many systems and sub-systems being pushed to the aboslute edge that can have issues in time attack. This is the part that sucks about competing with production based cars. If it were a factory developed race car (e.g. 997 GT3 Cup), then the builder or manufacturer will have already addressed every potential issue and a team only needs to buy replacment parts in case of failure. In a situation like the Sierra Sierra EVO, the team not only has to setup the car, but they need to engineer and validate solutions themselves. What a pain in the ass. Anyhow, I can count on one hand the number of times the EVO has come off the trailer and it ran one full day with little to no issues. Actually make that 3 fingers.

There were multiple WTF?s throughout the day, but the first and second "WTF?s" were the exhaust manifold bolts holding the turbo to the exhaust manifold. While we've never had that kind of problem in the past, the hardware was changed for ease of turbo removal and installation. The original hardware was race car style hardware: Unbrako socket cap screws (allen bolts), drilled and safety wired so there was no chance in hell they could back out. Since the screws were a bitch to use with the Garrett T04 and Full-Race exhaust manifold combination, some Fastenal brand grade 8 cap screws (hex head bolts) were used. They failed in about 1.5 laps when Emp called in on the radio complaining of a loss of power. In the hot pits, we saw the turbo was hanging off of the exhaust manifold. This was strange because Mike drilled and safety wired the bolt heads.



The cause?  ALL 4 bolt heads separated from the rest of the bolts at the same time. All four breaking at the same time is pretty ridiculous so it was determined to be a faulty batch of grade 8 screws. I don't exactly remember what happened next, but if I remember correctly, a different brand of grade 8 bolts were used and we had a similar failure in another 1.5 laps. That was WTF? #2. Sure the Unbrakos are a little more expensive, but they are worth the extra cost. Most of the socket head cap screws used on Cosworth race engines are Unbrako brand as well. We were reminded of the Christine Constant: if you've never experienced something before, you will for damn sure with this car. Here was the solution:



There weren't anymore of the right size Unbrako screws on the truck so the solution was to use some high grade studs from a drawer in the truck, crank on some nuts, and tack the fuckers in place. Problem solved as long as we didn't have to remove the turbo again.


Page 1 of 3 Next Page
Bookmark and Share
Tuesday, October 12, 2010 3:26 AM
Glad the car and the Emp were okay after that last WTF incident. Losing a car like that would have been terrible. Though that makes for some pretty interesting and badass pictures. Also very stoked to see what BW comes out with in their new turbo line. Mostly curious about price, all this engineering and clean sheet thinking HAS to come at a price, and hopefully it's within reason. If they can whip up a modern, more reliable GT28-equivalent for only a few hundred more than than the actual GT28 I have now, it would be worth looking at an upgrade.
Tuesday, October 12, 2010 3:28 AM
The reason for the failure of your Grade 8 bolts is that carbon steel MASSIVELY loses yield strength at higher temperatures. It is pretty much junk beyond 600-700 deg F, and a turbo fastener will reach much higher than that.

The solution is to use a nickel superalloy and a nut that will hold up to the heat(again, not carbon steel). Inconel 718 or A286 would both work for a stud material. In fact, I've heard that Nissan OEM turbo studs are some form of inconel, but of course have no way to confirm that(they seem to never break, so maybe worth looking into).

I recently had a problem where I had some carbon steel locknuts mushroom out on me on track with my SR20DET. I'm going to go with some titanium locknuts and hope they don't gall up on me. A nickel superalloy would be superior, but I couldn't find any metric nuts made from a suitable material.
Tuesday, October 12, 2010 3:37 AM
This is a good example of the material strength reduction at typical turbo operating temperatures(800-900 deg C).


The problem with using a regular austenitic or marstentitic stainless steel is that you are going to likely anneal the material, so the actual yield strength is going to drop to the 35-40 ksi range at room temp. You lose all the strength benefits of work hardening the fastener during manufacture, and end up with a ridiculously soft/weak fastener over time. But the above graph does give a pretty good picture of just how poor regular carbon steel is in this application.

I'm honestly surprised the Unbrako socket cap screws or studs lasted, but you were likely having to change them before they got too many fatigue cycles on them.

Eric Hsu
Eric Hsulink
Tuesday, October 12, 2010 6:03 AM
Def: the Unbrakos lasted quite a while and were even re-used. The Unbrakos are really that good and they never cease to amaze me. We made the assumption that since the Unbrakos could last, then Grade 8s would last as well. Oh well, live and learn.

I forgot to write that we did find a long term solution. Brock at BorgWarner supplied SSE with inconel studs and silver plated nuts. We have a bunch of inconel hardware and silver plated nuts at Cosworth as well (from the Champ Car engines), but just not in the sizes that Sierra needed. The silver plating prevents galling.
Eric Hsu
Eric Hsulink
Tuesday, October 12, 2010 6:18 AM
As for my statement above that Unbrakos are really that good: I'm not saying that one should ignore material spec when selecting a fastener. What I am saying is that Unbrakos seem to exceed their spec time and time again.
Tuesday, October 12, 2010 6:45 AM
Can't wait to see the new BorgWarner stuff. I am going to assume that seeing a Subie engine and the text "Cosworth will be both distributing the EFR turbo line and using them in a few new products" means Subaru parts (so please do not take my dream away).

I also saw that Full-Race is working with BorgWarner as well on the EFR turbos. Any collaboration?
Tuesday, October 12, 2010 7:59 AM
I agree Unbrako bolts routinely exceed minimum UTS limits. I'm a bit surprised they lasted as well, but as they say, specs alone don't mean something will work.
Tuesday, October 12, 2010 9:38 AM
Eric, I'm not an engineer; so I'm not gonna make some BS assumption.
I'm pretty sure you guys have used/ are using Cosworth head studs.
Have you tried ARP? Or analyze them/ compare them to the Cosworth one?
I bring this up because, as you already know, ARP makes some tough L19 headstuds (I can't remember the tensile strength on top of my head). I think if I remember correctly they can withstand around 80 psi of boost.
I thought, maybe the tensile strength of the Cosworth head studs is similar to the regular ARP one. (If I'm not mistaken the regular ARP one are rated around 180-200,000 PSI).
Anyway, just a thought.
Tuesday, October 12, 2010 9:56 AM
Eric I got another question for you:
Any reason why you guys switched from the VP MS109 to the E85? I'm sure price is not in the equation.
How about some higher octane/ leaded gas?.yeld more power while running cooler....no?
Tuesday, October 12, 2010 3:00 PM
The weight of the exhaust piping hanging off the turbo is a possible (if not probable) cause of all your failures. Not a new problem in the evo world.

And to JDMized, the power potential of E85 is MUCH greater than MS109 (on the order of about 100whp on this car). It's closer to a C16 or Q16 equivalent.
Eric Hsu
Eric Hsulink
Tuesday, October 12, 2010 3:29 PM
x01011000x: Yes we're working on some Subaru turbo products at the moment. We're mostly in the testing and development stages right now, but there will be a preview of some kind at SEMA. Yes Full-Race is also working with BW as far as the EFRs go. No, there's no direct collaboration at the moment although we're all friends. We do use some FR manifolds for certain engine tests. As for the turbo systems/kits we aren't targeting the same customer base as FR although there certainly will be some overlap.

Alex: I think the ARP 8740s are 190,00psi and the ARP2000s are 200,000psi. The L19s are rated at 260,000psi. The Cosworth H-11 studs are also up there at 260,000psi, but with the added benefit of the "dog tooth" at the bottom of the stud to preload the stud in the block (like a proper race engine stud). Sometimes its a matter of fastener strength, sometimes its a matter of cylinder head deflection, and sometimes its a matter of cylinder head bolt location. In this case its a little of each.

Alex: We switched from C16 to MS109 first because Australian CAMS (the equivalent of SCCA or FIA) @ the World Time Attack does not allow leaded fuels. Then from MS109 to E85 because of its power potential. But we didn't switch to normal E85 from the pump. Sierra Sierra happens to be right next door to Bentley Fuels who can supply SSE with a regulated, non-seasonal formula of E85. This is something that almost all of the street car guys overlook, but more on this later. I'll be writing an article on E85 soon.

Jamal: Have you had actual contact with the Sierra Sierra EVO exhaust or is that complete speculation? Speculation is not a new problem in the internet world. The SSE EVO's exhaust is quite light. Welding a v-band flange into the slip discharge channel and having the weld fail is also a known problem amongst those that work with T04s and those that do not use the correct procedure to weld alloys to cast iron.

In this particular case the E85 did not offer an additional 100whp of power potential. It greatly depends on an engine's VE, turbo efficiency, intercooler efficiency, exhaust flow, plenum design, etc. To put a label of 100whp power potential on a specific EVO without knowing the details probably isn't going to be the most accurate statement.
Mike Kojima
Mike Kojimalink
Tuesday, October 12, 2010 3:33 PM
Maybe try shower injectors to take advantage of E85's latent heat of evporization.
Eric Hsu
Eric Hsulink
Tuesday, October 12, 2010 3:38 PM
It's methanol that has the massive increase in latent heat of vaporation. E85 is better than gasoline, but probably not enough to warrant the change in injector positioning. Methanol would be the bomb, but it isn't allowed anywhere else except the US.
Tuesday, October 12, 2010 4:58 PM
Well, I've seen the car in person a couple of times and I'm looking at all the up close pictures of the manifold and turbo in the previous articles and I don't see any support structure. Lack of any brackets is a cause for failures such as these.
Mike Kojima
Mike Kojimalink
Tuesday, October 12, 2010 5:21 PM

E85 is still 40% better than gas.
Wednesday, October 13, 2010 11:42 AM
Another fantastic peak behind the scenes at one of the top time attack teams in the World! Great write-up Eric!

Wednesday, October 13, 2010 10:03 PM
Thanks for the reply Eric.
Yeah I looked up the H11 studs, but couldn't find the tensile strength.
Anyway, maybe, and that's a big F!@#$% maybe, the 4G63 block flex some, and cause the gasket not to seal properly.
If I recall it right, I read an article a while ago on some import tuner mag. (I can't remember the name) about how the Cosworth gaskets seal compare to other gaskets; interested reading.
As far as the gas choice, I had no idea the Redline folks wouldn't allow leaded fuel.
Is E85 the only choice left on the table? Aside from methanol or nitro, is there any other blends that would work for your application?
I keep thinking about heat and how it destroys stuff (crack the flange of the manifold and so forth).
Does Full Race use 304SS or 321 for their manifold? Inconel would be nice, but price wise....
Anyway, I'll probably see you at Infineon.
Eric Hsu
Eric Hsulink
Wednesday, October 13, 2010 10:20 PM
Jamal: I re-read what I wrote and it sounds like I was chewing you out. My bad, the dick head part of me got out (my friends will tell you that I am a dick more than half the time in person). Anyhow, for the record the SSE EVO's exhaust is solid mounted to the chassis, the engine mounts are solid, and the exhaust is very light so there was no lever action working on the v-band flange. I believe it was a weld failure which I've seen many times before.

Mike: I want to use methanol. I am envisioning some crazy shit I learned from studying Cosworth Champ Car engines. But if the car is to travel the world then we probably will not convert. We'll see about the E85. If 40% better latent heat of vaporization E85 vs. unleaded, what is unleaded's latent heat of vaporization? 40% of nothing is still jack shit. It may be better, but still jack. I've never studied it in great detail. Back with some Honda drag car stuff from back in the day with injectors near the top of the runners rather than shooting at the valves, switching from ethanol (E99) to methanol still gave MASSIVE gains.

Nik: If we ever get our shit together, we'll see you at a Redline event! (soon hopefully)

Alex: Redline allow whatever you want to run. It's the Australians and Brits that don't allow leaded fuels on track. The Japanese don't care, but good luck finding leaded race fuels in Japan other than the HKS Drug Gas (that's Japlish for Drag).
Friday, October 15, 2010 8:25 AM
Eric, no worries. But when you've gone through 6 turbos, broken the turbo off the manifold a couple of times, broken the exhaust off the turbo, you've got to take a little closer look at the causes. Just don't be surprised if you keep eating turbos.

We've been running a 35r right on the edge of the compressor map without an issue for two full seasons, after a chunk of piston took out the last one.
Sunday, October 17, 2010 9:23 AM
While inconel is a great solution for you guys, something that might help others out is that you can get threaded rod in Hastelloy alloy C-276 for a reasonable price. It is not as strong as many stainless steels at room temperature, but it maintains it's strength and is more resistant to oxide attack at higher temperatures. You can get Hastelloy C-276 hex nuts as well, although it may have galling issues, although I've heard it is no where near as bad as most stainless steels.

I wonder if E85 causes some hydrogen embrittlement issues in the inconel turbines?
Sunday, October 17, 2010 10:08 AM
I saw you allude to not wanting to o-ring the block. Are fire-rings/pyramid rings out of the question as well?
Sunday, October 17, 2010 12:28 PM
sounds like they'll be putting wills rings in there
Eric Hsu
Eric Hsulink
Sunday, October 17, 2010 5:15 PM
jamal: Here's some speculation on my part as to the reason why both GT35s and T04s failed. The original GT35s were just what I had to work with having taken over the Sierra Sierra engine program from another engine builder. I wouldn't have started out with something that small. It was fine at first, but as we gradually started increasing engine performance over time this caused the GT35s to fail. After upgrading to the T04, we also quickly approached and passed the edge of the compressor map as we turned up the power. This is all speculation since I've actually never run the car on an engine dyno at sea level. I only could rely on the Sierra Sierra Mustang chassis dyno which is at 4900 ft elevation, has a hyperactive correction factor, and as for uncorrected hp measurement accuracy....well it's a chassis dyno. Apparently I don't have enough BSFC data on the 4G63 for accurate hp calculation because we've never run a 4G63 on our engine dynos which are regularly calibrated. Chassis dynos are all over the place from unit to unit. I think I've been under calculating power output figures this entire time. Hence, we were running the compressors way off their maps as performance was increased.

mike156: good tip on the Hastelloy. The silver plating of any alloy nut really makes life easier for removal and replacement.

just_james: we considered pyramid rings, but opted for something a bit more resilient. I was told that in the early stages of the TRD 503E IMSA engines, they were using a double pyramid ring. But as the boost was increased, they ended up with a different solution. Copper wire o-rings has its place in the world, but just not in this kind of application.

jamal: we considered wills rings also, but opted for a solution a bit more sensitive to the 4G63's very flexible cylinder head. Most production cylinder heads distort like mad when asked to do something they weren't designed to do. They are basically hollow castings with a very thin fire face. Cosworth WRC had these problems with the Ford Zetec engine and Prodrive/Subaru WRC had these problems with the EJ20s. In WRC the factory cylinder head and block castings must be retained. They came up with some creative solutions that we benefited from. I think I'll be writing a full feature on the improvements in the future (if given approval). We did a quick test this past Friday at a local track in Reno and did not have any degradation of head sealing whatsoever. Needless to say, I was massively relieved.
Eric Hsu
Eric Hsulink
Sunday, October 17, 2010 8:49 PM
Since I wouldn't touch an EVO forum (or any other than MotoIQ's) with a 10 foot pole, I'm hoping somebody gets this to Dave Buschur in one form or another.

It's been brought to my attention that Dave Buschur's been taking my comments personally for some time now. For the record, absolutely NONE of it was ever directed toward him or Buschur Racing.

From my very first post about the Sierra Sierra time attack EVO, I only ever made a single mention of previous builders. In the first paragraph, I wrote, "After some engine troubles with other engine suppliers, SSE has teamed up with Cosworth to supply the engines, engine calibration (me), and turbos." That was it. There was zero mention of Dave or BR. I never dug deeply into what the problem was with the previous engines. I know that there was some disagreement between BR (the builders), and Haselgren Racing (the tuners at the time and the people who attempted to repair the BR engines). Since I didn't know what the actual situation was, I left it alone and I wrote my statement above. If I wanted to be an instigating dick, I would have called out Dave or BR directly by name, but not knowing the entire story, I simply reported the truth. To read this very first post on the Sierra Sierra EVO, CLICK HERE.

As for the copper wire comment above, it was also NOT directed directly toward Dave or BR again. There are about 50,000 machine shops out there that use copper wire stuffed into a groove. I have never laid an eye on the original BR engines and I have no idea how head sealing was addressed. My comment above was meant to explain that copper wire o-rings have their place in engines, but I don't believe that place is in a road racing engine.

I'm not really into bashing people or companies unless it needs to be done. BR has a huge customer base and David Koresh style following so I'm sure they do good stuff. They have plenty of experience doing what they do and build some crazy fast EVOs. If I was trying to talk shit about BR, I would have done it by name like I've done in the past to other companies.

I haven't read any of the posts on the Evo forums, but I've gotten emails and people calling me about it telling me to check it out. The forum world is something I don't care to be a part of. Selling shit or protecting my image on an an Evo forum is right there on my list next to climbing Mr. Everest (which will likewise never happen). I'm not saying I'm above it. It's just not for me and never has been.

Dave if you get around to reading this and want to discuss it, you can get my number from Mike Ferrara @ DSPORT and we can talk. Call me any time. If you don't want to call me no prob, but you can stop taking my comments as attacks. Trust me, I don't mean them that way.
Post Comment Login or register to post a comment.

MotoIQ Proudly Presents Our Partners:

© 2018 MotoIQ.com