ozconnection

Years ago I ran a JDM L20ET engine (without the turbo on it) in my car whilst my L28 was being rebuilt. It's a long story but what I eventually ended up trying was the turbo cam in my L28 engine built for normally aspirated use. When that cam was in my L20, the thing would rev out easily to 7.5K but when the L28 used the same cam, it was really torqey but ran out of puff at 5k. Same cam in two different engines!! Very different result about how they "felt" on the road. I couldn't believe it was the same cam in both engines. Yes, there is a whole bunch of difference between the two, especially noted items are comp. ratio, rod ratios and port/valve sizes. Less noted is ignition timing ie advance rate and static timing. To put it another way, there is more to changing the character of your engine than slotting in a cam. Its everything else around it that also influences its feel on the road. Cheers, Mark

That engine sound superb. Snappy+++ Cool I'm wondering what that hose is doing down near the oil filter, the looped one? I'm wondering if there has been sump/pickup position issues and you're using an oil hose to convert your LD28 block from front pickup to rear pickup?

Changing over to L24 rods and crank will change your rod to stroke ratio...this is true. Why?.... the theoretically optimum rod to stroke ratio is 1.75. The way this figure is calculated is to divide the length of the rod by the stroke of the crankshaft. L24 specs: 133mm/73.7mm = 1.80 rod/stroke ratio now, lets look at the L28 130mm/79mm = 1.65 These numbers reflect the inherent 'revability', the higher the number (like the L24) the higher the redline of the engine. On the other side of the coin, a lower number (like the L28), the more low speed torque is produced. It's a mechanical thing. Many papers have been written on the topic, so I will suggest you read some of them off the 'net. They will give you far more insight into what's happening inside your engine than I. The advantage you have in building such an engine is that H/D rods are available off the shelf (from Carillo for example) in this size. You are custom building pistons, so that's cool. There's heaps more in it, like the instantly lower compression for boosting using the same cylinder head, large valves compared to the swept volume of each cylinder and the H/d parts available. Cam timing shouldn't be an issue, and MSA has some bigger turbo cams if you need them. However, the stock turbo cam will work well if you so choose.Don't worry about capacity, wind in a little more boost, that'll cover it!! Interesting project, I considered something like this for my P230 Cedric, instead using an L20A crank I have sitting in my shed. BTW, that rod to stroke ratio works out to be 135mm/69.7 =1.94. Easy 8k rpm motor there, if it was built correctly, of course! (valve springs, rockers, port sizes, good quality valves, pistons, bottom end balance, flywheel material etc etc etc) Good luck mate with your project...

Does anyone else feel like me on this thread? I thought I knew a little bit about cars but it seems that I have been fooling myself for far tooooooo long. (I must have missed something....buggar!)

There is a very good book that attempts to give its readers insight into what is really going on in an engines cooling system. The book is "Four Stroke Performance Tuning" by A. Graham Bell. Chapter nine, Lubrication and Cooling discusses the do's and dont's of cooling systems. It's a bloody good read and well worth buying or borrowing from your local library to do some research. 'ARGH' is pretty much what the author had to say about removing thermostats too, don't do it!!!! It does talk about things like fans and shrouds, radiator fin counts, materials used ie aluminium pump types and mods for increasing flow etc. I have adapted many of the ideas in the book to my L28 which runs an auto trans and air con in the hot Aussie summer and it hasn't let me down yet!! Nothing too radical, just basic and solid engineering. Good luck with your cooling system, Cheers:smile:

Supertip, Here is another shot of Dave Smiths engine bay. I hope this helps you out. Cheers:mparty:

Supertip, That 'round thing' with the wire coming from it on top of the intake manifold closest the distributor is a Hobbs switch, used to activate the water injection when the turbo spools and boosts the engine above atmospheric. I've had a few on my old engine, and they're adjustable. You can set at what boost pressure things are turned on and off. Handy little buggars! I don't get what you mean by recirculating BOV....from where to where?? The plumbing that I can see in the photo doesn't look that complex. I'll try and look for another photo of that engine from another angle to see if "All can be revealed" Stay tuned! Cheers!

Supertip, You're right, it seems dumb to be running a BOV because of venting air and fuel into a very hot area with the exhaust housing being so close. Option 2: wastegate! (maybe and perhaps more likely). The hoses? I think that has them all covered, dunno what else they could be attached to. Cheers.

Supertip, The looped line looks like it might be connected to a blow off valve? The other one is probably for the brake booster, we drive on the other side of the road down here, same as the UK. One line attaches to the weber manifold adapter, which is a water injection line, needed because this setup can't be intercooled conventionally. The other one is an oil feed line to the turbo. Unlike an EFI engine, this is super simplesetup and probably reasonably effective! I hope this helps you out a little. Cheers.

Supertip, That manifold adapter that Dave has on his engine was a 'one of' built by a mechanical engineer who designed the manifold himself when the car was still his. The weber adapter doesn't look too special. Fairly easy to knock up if you have the time, talent or money to get it done for you. Cheers.

Found this in my picture archive. (The picture is not mine and belongs to Dave Smith). I thought this might give you some ideas about adding a weber to your turbo engine.

I liked the idea of a turbo'ed carby 4 barrel setup but the cost of a suitably prep'ed Holley for blow through made me think of a fuel injected throttle body instead. This is what I have gathered so far, I think you guys can see where I'm headed? BTW, this engine will eventually ride in something that looks like this. (see attached picy).