+1! Too bad the old block is toast
I really hope the new config works much better on track so that Patrick and Paul can get good results in the coming race

 

Yes, I've heard those same figures in the past... a few thoughts though:

1. These are "acceptable" or barely acceptable compromises rather than what is optimal whereas you are really looking for a more optimal result.

2. They are also very general type comments and do not take into account the specifics of your engine such as big cam where you should have less back pressure vs small cam where back pressure is not as critical.

3. I think they are probably a little outdated since turbo design and efficiency has come a long way since these back pressure ratio figures started being bandied about.

Is it some form of JME 304M2/296M camshaft you are using? If so, I'm sure Jon would be in the best position to advise of optimal back pressure, what's acceptable, and what you'd lose in the compromise between optimal and acceptable.

 

Just a quick thing to add. The water pressure shown on the Motec readout was in fact Xover pressure. I didn't realise that they'd swapped the sensor in this case. So we saw max 50psi backpressure at 26psi which is pretty much bang on what was recommended.

We took the head off today and found some concerns. There were signs of heat in the copper gasket and deckplate and some copper transfer onto the head too. As in small fragments probably due to typical 'shivering' when the head lifts. We're going to try a different sealant and probably go with the Evans coolant. Will also be making some holes in the gasket larger to allow better water transfer between head and block. Hopefully that will help.

Yes, we can try the .82 house too, but for next weekend we will stick with the .63.

 

I work out more or less accurately from the log that you are reaching the back pressure/boost ratio of 1:1 several hundreds rpm before reaching peak boost. At 7k rpm the ratio peaks more or less at ~2:1 without increasing anymore.

A ratio of 2:1 is probably too much for head studs to handle with a high overlap cam on a CR of 9:1 with 25+ psi of boost and an accordingly sharp ignition curve.

 

Patrick...
Have you considered a VGT/VNT? Seems it would work pretty well with your throttle-controlled boost levels.
And those things have huge hotsides when wide open.

I imagine you guys got the Ford Powerstroke diesel V8s down there (7.3L/6.0L) so there should be some turbos laying around...and a huge aftermarket for turbo wheels...just a thought.

 

We don't have those cars here. Only good turbo engines we've got are the for Xr6 turbos that come with gt3540 on them basically a gt3582r

 

those were the engines in the F-250/F-350 since 1998...didn't get those?

 

Nope. big 'trucks' aren't necessary here. we're a sports sedan country and utes.

 

Actually, I think there's a few around, just nothing like the quantities over there. Ford stopped bringing in F series some years ago so they are ridiculously expensive and quite scarce.

I think that Garrett DualBoost is really quite brilliant... here's a link:

http://www.internationalpowerstroke.com/sst.html

Couple of problems though (I actually spoke to Garrett about them):

1. They are huge and so much bigger than what you'd ever use for a petrol engine looking to produce around 500 - 600 HP. Garrett said they weigh around 15 kg... by comparison, a LR Super 75 weighs around 6 kg!

2. Being designed for diesel, they are limited in the egt's they can handle reliably... Garrett says egt's should be limited to 800 C.

Apparently Garrett does now have a DualBoost turbo for petrol with axial turbine... but alas, it's more in the 250 HP range:

http://turbo.honeywell.com/our-techn...turbochargers/

http://turbo.honeywell.com/assets/pd...esentation.pdf

 

So a bit of an update with this 2.5 8v motor. Despite some changes prior to the one and only race weekend, we still were lifting the head. We haven't used the motor or car since April. The motor was stripped down and a light decking done to ensure a perfectly flat surface. We ordered a new copper gasket and set of firing rings. The intention was to go back to the .82 housing to see what differences we'd find. Unfortunately the 16v motor won't be ready in time for this years WTAC so we are reliant on this little racemotor giving us a chance at challenging the favourites.

Paul and Sean were putting it back together yesterday and they'd torqued the headstuds to 30ft/lbs and when they went to do the 2nd round of torquing to less than 60ft/lbs..this happened. Possibly a problem with the combination of large headstuds and 25+ year old Alu blocks. So down comes the motor again and back to the machinists to begin Timesert'ing the block. It was mentioned to look at Keenserts but from what I can see, they don't seem to be available down here. Has anyone used these and have opinions?

 

Patrick...
Do you ever feel like you should have just filled a trash can with dollars and set it aflame?

Rotten luck!

 

Ive used a "recoil" kit before on my block. but only for small threads. similar but the insert is just a tread that looks like a spring that expands. The Timesert looks like it'll be stronger.

Possible to use larger studs on the block?

 

It amounts to the same thing Spence. I just shovel money into the pit and never drive this thing.

Not really possible. These things are massive as it is. We're going to get some Timeserts made up and also have a custom thread tool thingy made. I spoke to someone here about the Keenserts but he wasn't so keen on them. They sell a product called Bigsert but they aren't Big enough for these studs. (End of word association puns now).

 

No use on getting a custom Tap (thread tool thingy) when you can use an existing thread size. For example IICR the head studs are M12 x1.5 you could make a "timesert" for the inside thread M12x1.5 and the outside thread M16x1.5

Saves paying for a new custom Tap (could be around $100+ for 1 tap) that'll have one use only.

 

Paul is going to get it sorted by all reports. Just more frustration / costs...but it seems pretty standard for the territory.