hookie

iTrader: (17)

Hi guys after a bit of info,I have bought a p1 engine to build upto 400hp,I curently run a type r v4 running 320hp with mods and is very reliable.Now the engine thats already in the car is a open block ? the engine I have bought is a open block or are they both semi open ? and is the open reliable up to 400bhp with suporting mods....Many thanks Andy

Ian

iTrader: (10)

i this it is a open block, and on standard interinals etc you are pushing it at 400

hookie

iTrader: (17)

But with non std internals can I get my open block up to or arround that figure being sensable about it

Ian

iTrader: (10)

yes

there are a quite a few people running 380/390 bhp

hookie

iTrader: (17)

Cheers mate for your info (top man).....Andy

harvey

iTrader: (48)

Lots of open deck blocks run well over 500 bhp. Block strength is generally not a weakness.

samcowrx

my open deck is running 1.5 bar 380bhp happily.

sponners

iTrader: (4)

thats what I thought.

....how many people on here have heard of block failures due to it being open deck???......I bet not many at all.

and on a plus side, better cooling.

samcowrx

Definately easier cooling on an open deck, what is the rumour at high boost levels concerning open decks?, cylinder walk and head gaskets failing as a result?, i think i read that somewhere? Yet to see it happen at 1.5 and 1.7 bar.

silent running

And I've had a CDB apart with a spun liner but no other signs of movement. Very weird.

harvey

iTrader: (48)

I have heard stories of cylinders walking on open deck blocks but think it is part of the Scooby myth. When I first got involved tuning my STi 6 Wagon a number of experts told me it would be impossible to get 400 bhp from 2 litres and even if you did it would need a closed deck block and the car would not be driveable. As is now well known the experts got it wrong. I have plenty knowledge of 550 plus 2 litre open deck blocks running 1.8 to 2 bar without any apparent issues. OE fuel rails. OE head bolts etc. so the standard engine, certainly version 5 and 6 STi is a lot more durable than many people give it credit for.

Mus

iTrader: (2)

thats very intresting i thought closed deck blocks were the most durable!

dynamix

iTrader: (3)

Harvey's not saying they arent.

Are you sure about the OE head studs Harvey ?


There are a lot of myths .....

harvey

iTrader: (48)

The cars I am aware of, at this power level, with standard head bolts have had no head issues or other engine issues for that matter. This is not the case with 2.5 litres.
I think the closed deck block will be stronger in terms of rigidity and cylinder security but what I am saying is that the open deck block, in my experience, copes OK at close to 600 bhp. 2 litre block failures, as Spooners says, are quite uncommon.
These 2 litre engines, built and treated properly, are far more durable than most people realise. Some suppliers selling fuel rails and such like will encourage customers to buy these for 400 bhp projects or whatever, when clearly they are not needed. Consequently a lot of people spend way over the top on modifications they do not need. Good for suppliers if that is what they want to do. Also lots of crap advice or downright impractical from friends of friends. I recently had a guy convinced that fitting a rotated turbo kit was the way to go for improving spool. When I asked what turbo he was planning to use, he replied quite seriously that it was a TD05 16G.

Going back to the CDB, it is a big lump of aluminium so it may not be a good engine to subject to regular cold starts and shut downs as the stresses from thermal expansion are probably far far greater than with an open or semi deck block. I have no evidence to support this but others may have some observations.

jayallen

iTrader: (31)

I read an article a couple of years ago about the CDB. It said that early Subaru tuning theory was to use a CDB for big power builds but due to continued improvements from the factory the CDB, even tho still desirable, was no longer as important as they were.

Mus

iTrader: (2)

my understanding of semi closed deck that you cant run over 2 bar of boost as it will cause head gasket problem, thats why i'm going to a closed deck. am i on the right lines here?

dynamix

iTrader: (3)

I dont think that is right.

Semi closed deck block here running 2.5 bar of boost. Shaun also does similar on SCDB.

JP4

iTrader: (12)

Harvey - what are your views on Rotated Turbo Kits/set ups? Are these the way forward say when using larger turbos i.e GT35/40 to give a quicker spool up?

As apposed to CDB, what are your views on say converting a 2 ltr block to 2.2 stroker/2.33 so as to get best of both worlds ie revebility and torque?

Mus

iTrader: (2)

so semi closed deck is better all round block

samcowrx

Yes, it is the one to go for, for big builds, its a good starting point.

MartynJ

I'm sorry but I don't agree, the closed deck block is the one to go for on big power builds, always has been, always will be.
RCM 2 litre, Andy F 2.2 litre, Area 52 (Jasons car) 2 litre and my own 2.1 stroker. We can't all be wrong ! Lol.
I deliberately chose the CDB even though I had a perfect semi closed deck block too.

That said there are plenty of people of running big power on semi closed, but I have never heard of people having problems with their engines due to them being closed deck.

harvey

iTrader: (48)

This is not what I am saying. Please read what I have writ.
An open deck block is far more durable than many people appreciate and I have experience of these in the 500 to almost 600 bhp bracket and they performed/ are performing without failure. There is no history of block failure but using a CDB must remove a potential weakness as power expands beyond the unknown limit for an open deck.

As for rotated turbos, these are a good idea if you want to fit a turbo that is too big for the conventional mounting. Conventionally mounted turbos can do up to around 600 bhp. I see no point going this way unless you are running big power, certainly over 500 bhp. The big downside is the expense. Completely different uppipe, downpipe set up, separate wastegate valve etc. Not for the faint hearted and probably not necessary for 90 odd percent of Scooby owners. Benefits are better boost control for a start. I believe in like for like situations it will be more efficient but cannot prove that or quantify the difference in efficiency at present but I am looking at that now so will have factual knowledge during early 2009.

What engine is best for you depends what you want to do with it. A 2 litre has far better VE than a 2.5. The 2 litre suits RCMS for the purpose for which they use it while others achieve good results with a 2.5. The 2.5 with comparatively big torque for little effort by virtue of it being a 2.5 litre is very easy to drive around town, pulls from low down, responsive, fair turn of speed so attractive to a lot of petrol heads now that it has been around for a few years and pitfalls learned. In my opinion it is not yet a cost effective route to winning races with reliability which the 2 litre is.
2.2 does not figure on my radar but time permitting I may have a look at how a 2.38 litre performs during the coming year but finding time to do all the work in progress is proving difficult. It will be CDB simply because I have the block already and if things go well it will produce more power than any other open deck I am aware of at present.

Martyn.
You are probably right but in my opinion no need for a CDB unless you are going a long, long way past 500 bhp on a 2 litre.

Martyn.
No disrespect to some very clever people but I don't share your logic. One of the cars is probably around 700 bhp and over 800 bhp with nitrous so anything that can be done to remove a potential weakness at that power level is desirable so a CDB is certainly advisable. Remeber that some years ago the "experts" told me when I was new to the Subaru scene that 400 bhp was impossible with my 2 litre STi6 Wagon and even if it could be achieved it would take a CDB and would be unuasble for daily driving. When that milestone was achieved (in public) I was then accused of cheating!!! Some time before that the alumni were convinced the world was flat.

BTW I should add that I was advised by Matt Clark, just last Friday to stick with the semi O/E block of the 2.5 litre for a build well over 500 bhp. I had planned to reliner the block and strengthen but Matt was adament this was not needed and pointed to several high power big 2.5 builds they had done.

MartynJ

Harvey, good advice as always and it is good to see you back and fighting fit.
I was however just pointing out that the semi closed deck block is in no way better than the CDB.
Given the choice at the same money, which would you choose ?
I made my choice based on the above.

Mus

iTrader: (2)

sorry for the confusion boys i was just a bit shocked after reading one of the posts i think i miss understood it cause i just forked out for a closed deck block.

mus

MartynJ

No probs Mus, you just carry on m8.

samcowrx

Sorry my reply in that post was aimed at cdb, not scdb.

harvey

iTrader: (48)

Mus : I assume Neil built your engine or is building it now and by choosing a CDB he is leaving no doubt that the block could be a weak part in the jigsaw but as already said there are lots of 500 bhp plus open deck 2 litres of proven reliability.
Martyn, I think we are both generally of the same opinion but for me I would not automatically choose a CDB and if it is an engine that will have lots of stop start journeys and hence unlikely to be a big power engine I would be more likely to choose an open or semi open deck. The semi open deck must have a lot going for it in 2 litre configuration.
Thanks for the graphs. 2.1 litre torque at only 1.2 bar is impressive. What boost do you plan to run it at?

JP4

iTrader: (12)

Harvey - Many thanks for your thoughts on the rotated turbo route - much appreciated fella.

Its threads like this which really invokes thought processes and feedback from the likes of both Harvey and MartynJ - good on you chaps!

Mus - thought you were giving up on Scoobs?

R4LLY

iTrader: (1)

I think the pics got to him JP

Mus

iTrader: (2)

jp4; i was in a verge of braking it due to the credit crunch and buy something for me and my other half to share, as the days went on every day i see it on my drive cant drive cant start it, every weekend the boys are out cruising or going to meets believe me its hard.

harvey; yep neil at slowboy is building it for me i got confused i was told by a close friend of mine something about open decks and i confused it with semi closed deck.lol im hoping to have it out by end of january.

R4lly; don't worry my dear friend your time will come.

what can is say every day you learn something new.