New Porsche race engine. Checking on suggested oil.

[SHARKYTOOTH]

Bit of an unusual race motor. Car started as a 1986 Porsche 944 turbo. These come standard with a 4 cylinder 2.5lt single cam 8v and made 250bhp in the later models. Car has been developed into a pretty highly developed Time Attack / Race car. The motor is now 3.2ltr 16v with a forged internals, solid tappets, EFR 9180 turbo. Last time it went to the dyno it made 618whp @ 16psi which is pretty promising. However the block cracked causing an engine fire and I had to source a new block and decided to go with Darton MiD sleeves. They provided a custom copper head gasket and I sourced some hard to get big studs. The head is clamped down 120lbs. The studs were a late addition. When they installed these they expected to have to do a re hone of the cylinders. But they stayed perfectly round which shows the integrity of these sleeves. My concern is with variance in expansion rates but these guys come highly recommended and that's what they suggested using when we sent them the new block etc.

The machinist who installed the sleeves and repaired the head suggested the following:

"Run with JOE GIBBS BR30 or BR40 Break-In oil ONLY on dyno until rings are bedded in. Dump oil, cut oil filter and check.
Run a mineral oil for first 1000km then service and use recommended weighted oil (refer to engine build sheet for bearing clearances and Joe Gibbs oil recommendations"

He then recommended one of the XP6 variants and sent a oil spec sheet to choose from. (Attached) The motor is an Alu block now with ductile iron sleeves. Custom CP pistons and Carrillo rods. I was a little unsure which oil to pick so I contacted the company. This is what they replied:

"I chose the GP-1 15W-40 for a couple of reasons. The 15W-40 is a better fit for your main bearing clearance, your front and rear bearings were a bit tighter than the rest, but I would recommend going to the heavy side in line with the centre mains.

I did not consider the XP for your application because the XP has very little detergent and virtually no corrosion protection package. XPs are formulated for applications that are disassembled and inspected after every event."

I also managed to communicate with Lake Speed (that oil guy) who recommended the GP-1 20w/50.

I've also attached the engine build specs. As to the tighter clearances on 1 & 5 this is what the machinist replied:

"The variation in main clearance is due to bearing shell wall thickness variants. The tighter clearance on #1 & #5 is not a concern as it is still sufficient clearance and well within manufacture specifications and .0005" larger than minimum."

Sorry for long winded thread. The car is due to the dyno in the next few weeks and we're just deciding on the oil. I'm sure there are some highly experienced people inside these 4 walls who can offer some expert advice.

Thanks in advance.

 

[Jetronic]

If you get the oil and engine decently warm before racing (why wouldn't you?) there's never any harm in going to a higher viscosity. Going lower viscosity might save a few HP but you do risk damage. The thinner you go, the higher the risk.

I'd likely go with a 20W-50 aswell. A synthetic one, preferably PAO/ester blend. Is the car trailered to events? In that case true race oils are an option.

 

[rstcso]

Sounds like the engine builder is doing right by you providing all the data and their recommendations. I see no reason to second-guess them.

Here's a link to Lake Speed Jr discussing choosing the right viscosity, specifically using Driven oils.

Congratulations! That's going to be a lot of fun. Please keep us posted so we can live vicariously through you.

 

[SHARKYTOOTH]

If you get the oil and engine decently warm before racing (why wouldn't you?) there's never any harm in going to a higher viscosity. Going lower viscosity might save a few HP but you do risk damage. The thinner you go, the higher the risk.

I'd likely go with a 20W-50 aswell. A synthetic one, preferably PAO/ester blend. Is the car trailered to events? In that case true race oils are an option.

I totally agree. We always used to go with VR1 either 20/50 or 25/60. The car started off as a streeter and gradually got built into what it is today. It moved shop and they were using a 60w race oil which I can't recall what brand. With the new block/sleeves I'm not wanting to do anything that puts it in jeopardy or not cover my ass should anything go wrong. I've had a lot of engine problems over the years and almost always carried the can. So, I'll be going the thicker viscosity for sure. I just wasn't quite sure which model as the machinist said one type and the company + expert said another. I've never used this brand either but I've only heard good things.

Yes, car definitely only trailerable. We can't drive caged cars on the street Down Under.

 

[SHARKYTOOTH]

Sounds like the engine builder is doing right by you providing all the data and their recommendations. I see no reason to second-guess them.

Here's a link to Lake Speed Jr discussing choosing the right viscosity, specifically using Driven oils.

Congratulations! That's going to be a lot of fun. Please keep us posted so we can live vicariously through you.

The previous engine failed so early in it's life that we could retain pretty much all the internals. That was supplied by a builder in California at great cost to me. So when we had to pick up the pieces after that happened I was directed to someone closer to home (Down Under). They are machinists and builders. I just don't quite know why he said to use the XP model when the company itself and the expert both suggested the GP-1.

The other part of the question was the brand itself (Driven / Joe Gibbs) which I've never used. However it seems that they have a good following. I was just Googling around and happened across this site so I thought I'd throw it to the panel as such.

As for the car, it's pretty amazing for what it started as. Like many (non factory built) race cars, they begin as normal road vehicles and we take them to the track to do what we call Club racing. This is like your HPDE days but competitive against the clock and others in your class/speed groups. People drive their cars flat out and this is of course when you start down the slippery slope of trying to make them go faster. Once this car had got to a certain point I decided to put a cage in it for safety and that's when it becomes a trailer car down here. So the slippery slope gets ever steeper and you wind up with a car weighing about 2500lbs capable of well over 700bhp and a fair bit of quality aero going on. We still run on street legal rubber (Yokohama AO50) and it still has a factory 6 speed H pattern gearbag. It laps our local track around the same time as a factory Porsche Cup car and we can go a bit faster. The biggest thing holding it back is not having a sequential transmission. We're allowed to run them but for this car I have to come up with $50k+ to buy and have it fabbed into the car. It's just too much out of the sponsor's budget (my back pocket). The next person who buys it will be getting a bargain and should be able to afford to upgrade the transmission.

 

[thastinger]

Those are some nice pistons and rods.

 

[Cujet]

This brings back some great memories. As a second career, 30+ years ago, I worked (as a contract tech) for Leigh Miller Racing here in the Palm Beaches. Due to my previous professional race car career with various companies, I did a little bit of everything for them assembling cars, including some work on the turbo 968 for the 12 hours of Sebring. Although I did not build or configure the (3L IIRC) engine, I did help them with dyno boost related issues. As the dyno tech was unfamiliar with the setup. Once I got the boost dialed in, the engine was just shy of 500HP (again IIRC) And I fabricated the car's exhaust system from 4 inch sewer pipe

Overall, here is how I see it. Today, we have some stunningly good lower viscosity oils that can protect race engines very well when temps are managed exceptionally carefully. This is do-able and is being done by the pro's. For the rest of us, oil temps are exceedingly difficult to manage properly at say 180ºF (and no more for lower viscosity race engine oils), and a failure here translates to engine rework.

The high output turbocharged 4 cylinder engines I worked with in a past life, some of which were in the 550-750HP range, M1, 15W-50 was common and eventually a switch to 20W-50 synthetic became a requirement. The oil temps were always a prob on hot days. Yes, we'd run down to WalMart and pick up Mobil 1 20W-50 V-Twin motorcycle oil. That stuff really is good for turbocharged engines.

Keep in mind, the dimensional changes associated with the aluminum block engine. As they expand and the main bearing clearances do increase. So if the engine builder set main bearing clearances at (like my friends Radical V8) at 0.0015 inches, a hot aluminum block engine will expand at least another 0.0015 inches. Leading to at least 3 thousandths main bearing clearance. Note: His radical engine must be pre-heated prior to start, and must still use a high viscosity oil.

Another way to look at the oil requirement is HP per cylinder. While not really a common method, it does help illustrate just how much load each rod bearing must withstand, and can help with oil choice. At 150 HP per cylinder, the rod bearing will require the very best of everything. I'd look into oils that have an HTHS in the high 5's or even 6.0 as a good place to start.

 

[Cujet]

Those are some nice pistons and rods.

I don't see pics of the rods. I'd love to see them.

 

[thastinger]

I don't see pics of the rods. I'd love to see them.

He said they were Carrillo rods with CP pistons. I don't see any gas ports in the tops of the pistons so maybe they are on the sides on his.

 

[SHARKYTOOTH]

Sorry for the delay. Different time zones.

Here's a few more pics of the engine. The one from the US had a deck plate to close the open block. After the engine failure we pulled the head off and saw that the deckplate wasn't flush in all regions across the top. We had two previous motors from the builder (3.1lt 8v & 2.6lt 8v) and noted that the deckplate had shifted on the smaller motor too. So in putting together a new motor down here we didn't go for another deckplate, however the MiD cylinders sort of do the same thing by interlocking and minimising cylinder movement.

So these various pics were sent to me by the US builder prior to me receiving the motor down here. The crank was offset and a small amount of weight removed. The stock cranks in these motors are pretty hefty.

 

[SHARKYTOOTH]

This brings back some great memories. As a second career, 30+ years ago, I worked (as a contract tech) for Leigh Miller Racing here in the Palm Beaches. Due to my previous professional race car career with various companies, I did a little bit of everything for them assembling cars, including some work on the turbo 968 for the 12 hours of Sebring. Although I did not build or configure the (3L IIRC) engine, I did help them with dyno boost related issues. As the dyno tech was unfamiliar with the setup. Once I got the boost dialed in, the engine was just shy of 500HP (again IIRC) And I fabricated the car's exhaust system from 4 inch sewer pipe

Overall, here is how I see it. Today, we have some stunningly good lower viscosity oils that can protect race engines very well when temps are managed exceptionally carefully. This is do-able and is being done by the pro's. For the rest of us, oil temps are exceedingly difficult to manage properly at say 180ºF (and no more for lower viscosity race engine oils), and a failure here translates to engine rework.

The high output turbocharged 4 cylinder engines I worked with in a past life, some of which were in the 550-750HP range, M1, 15W-50 was common and eventually a switch to 20W-50 synthetic became a requirement. The oil temps were always a prob on hot days. Yes, we'd run down to WalMart and pick up Mobil 1 20W-50 V-Twin motorcycle oil. That stuff really is good for turbocharged engines.

Keep in mind, the dimensional changes associated with the aluminum block engine. As they expand and the main bearing clearances do increase. So if the engine builder set main bearing clearances at (like my friends Radical V8) at 0.0015 inches, a hot aluminum block engine will expand at least another 0.0015 inches. Leading to at least 3 thousandths main bearing clearance. Note: His radical engine must be pre-heated prior to start, and must still use a high viscosity oil.

Another way to look at the oil requirement is HP per cylinder. While not really a common method, it does help illustrate just how much load each rod bearing must withstand, and can help with oil choice. At 150 HP per cylinder, the rod bearing will require the very best of everything. I'd look into oils that have an HTHS in the high 5's or even 6.0 as a good place to start.

Wow that's amazing that you worked on those 968 turbos. Very rare and short lived model. One of the very rarest Porsches overall. Did you get any pics of when you were working on the 968t by any chance? It was a shame the factory really didn't want them to succeed. If they did they would have developed it with the twin cam 16v head instead of making up a bit of a parts bin motor using a 3lt block and the 2.7lt larger 8v head. Teams were just so much more familiar with the rear engine racecars and they were supported and developed by the factory at a much greater rate.

As a comparison, I had a 3.1lt 8v motor built and we saw 550whp at 25psi. We got just over 500whp on the 2.6lt 8v racemotor too, but that was at 26psi. By comparison, with the 3.2lt 16v motor we saw 618whp at only 16psi. So the 16v head just flows so much more. This current head flows 375 cfm @ 28" /550 lift for example.

I'll have to look into what specs the Joe Gibbs oils have as far as HTHS. We do have good cooling. Run 8 injectors and race grade Ethanol fuel. PWR water to oil cooler and dry sump. Motec throughout and sensors everywhere.

 

[SHARKYTOOTH]

Here's a short video of it some years ago. Inside and outside the car. Very short rural track. But at the end when the car's up and going you get the impression that it's pretty quick. They're also very well balanced with the front engine/rear transaxle. Very under appreciated cars.

 

[CruisinIt]

Porsche looks good mate. The WTAC is an awesome event to go to. Last time I went was 2019 but aiming to go again this year.

Have you considered the Gulf Western Comp R 50 ? It’s a Racing 25w50 that’s supposed to be compatible with all fuel types. Some of the Top fuel dragsters use it as well. Best of all is you can buy it direct from Gulf Western at St Mary’s in 20L drums at wholesale price so value for money is there.

 

[SHARKYTOOTH]

Thanks mate. Yes, it's a great event. Gets bigger every year.

I don't know much about Gulf Western oils. I suppose at least there would be a connection between the brands if nothing else!
I'll take a look. Thanks for the tip.

 

[Cujet]

Wow that's amazing that you worked on those 968 turbos. Very rare and short lived model. One of the very rarest Porsches overall. Did you get any pics of when you were working on the 968t by any chance?

I probably have some film pics buried somewhere. Unfortunately, I'm packed up for a move, unhealthy and unable to complete that move in a timely manner. If I come across some, I'll post 'em. Was a fun time. I looked online for some pics and remember this one well (no I was not involved with this car) :

Your car looks incredible!!!!!!!! That is truly my kind of beast. What are the V6 cylinder heads from?

 

[SHARKYTOOTH]

I probably have some film pics buried somewhere. Unfortunately, I'm packed up for a move, unhealthy and unable to complete that move in a timely manner. If I come across some, I'll post 'em. Was a fun time. I looked online for some pics and remember this one well (no I was not involved with this car) :

Your car looks incredible!!!!!!!! That is truly my kind of beast. What are the V6 cylinder heads from?

Unfortunately I have a similar pic of my car back in 2017 when after the very first outlap the block cracked and caused an engine fire. Very fortunate that the car didn't burn to the ground.

Sorry to hear of your health issues. Seems more common than not these days. Getting older...it's for the birds!

Oh, the 6 cylinder head is just a pic sent to me from the previous builder to show the same multi layer gasket / garlock sealing rings. I should have stated that more clearly. We've now gone for similar fire rings but copper gasket.

ps...I noticed on another thread of yours re highest HTHS oils. I can't find a published figure for Driven GP-1 20w/50. I sent them a message and await the reply.

 

[Cujet]

Unfortunately I have a similar pic of my car back in 2017 when after the very first outlap the block cracked and caused an engine fire. Very fortunate that the car didn't burn to the ground.

Sorry to hear of your health issues.

Thx! Working on the health thing. I've used Grok3 with great results in troubleshooting and treating health issues.

Wow, that's one heck of a pic! One heck of a car. Interesting that a roll cage, a safety feature, makes a car track only down under. No issues with that here (that I know of) and I'm pretty sure nobody would care. How's the transmission (transaxle) holding up? I know someone with a V8 conversion and has had some issues there. His car looks a lot like yours. Black and tough. My guess is that his engine is far less powerful.

 

[JimPghPA]

LSJ did a YT video where in he talked about the Joe Gibbs breakin oil, and how it lays down the required coating on internal parts of high HP engines to protect them. It made a huge differance and protected their engines when other racers were having their engines fail. It actually helped them win many races. It's very good breakin oil. Probably the best that's made for that. Run it as prescribed. No less, and no longer, acording to LSJ.

 

[Hohn]

Just one (diesel) engine engineer's opinion, but I'm going with LSJr's recommendation of the GP1 20w50. Especially with an aluminum block, the static clearances are only a part of the picture. As @Cujet highlighted, it's the dynamic clearances that matter when you start yanking on those main and rod caps with literal tons of force. Who cares what the clearances are on a cold engine that's not moving? That's just a starting point. Add some heat and a couple bar of boost and a couple thousand Gs of acceleration on the reciprocating assembly and your running clearances will be triple or quadruple.

I think you want the higher film strength of a thicker base oil that reduces temporary shear.

IMO the question isn't whether to run 20w50 or thinner. Rather, it's whether to run 20w50 or a straight SAE 50 or SAE 60. I think the GP1 20w50 is probably the sweet spot for you in the Driven line.

I'm a valvoline guy at heart, though, so Black bottle VR1 20w50 synthetic is where I'd start as it's the safe option. It might not be the "best" choice but it's almost always a solid one.

Grey bottle VR1 SAE 50 would be an excellent choice as well and probably offers slightly higher MOFT in the bearings and on the stressed valvetrain parts. I think Valvoline have good distribution in Oceana too, so Aussies can source these oils quite easily at reasonable cost.

The ultimate choice would be the BARO from our friends at HPL, but I know shipping to Australia can be brutal, and it's already pricey oil.

PS: those head studs are sexy as it gets. Straight out of the NASA Fastener design manual.

 

[SHARKYTOOTH]

Thx! Working on the health thing. I've used Grok3 with great results in troubleshooting and treating health issues.

Wow, that's one heck of a pic! One heck of a car. Interesting that a roll cage, a safety feature, makes a car track only down under. No issues with that here (that I know of) and I'm pretty sure nobody would care. How's the transmission (transaxle) holding up? I know someone with a V8 conversion and has had some issues there. His car looks a lot like yours. Black and tough. My guess is that his engine is far less powerful.

I've not heard of Grok3. Sounds like the janitor from 'It's about time' lol. I'll have to look it up.

Yes, driving a caged car on the street here is pretty much illegal. Perhaps some vintage targa cars can get a temporary license to drive to and from an event.

I converted the trans from the 944 turbo to a rebuilt (California Motorsports) 968 6 speed. To be honest I've never liked the 6 speed as much as my old 5 speed in terms of precision of shifting. We also lose a lot of time compared to the cars with the sequential transmissions. We're converting to drive by wire and going to run an extra throttle body prior to the turbo to keep it spinning when off throttle or changing gears. Try to minimise the loss of spool up.