Dave W.

IMHO those holes allow a little extra coolant to flow up from the block and across the exhaust port on cyl#1. It's a good idea since the head of cyl #1 is last in line to get coolant and it's already a little hot in that area.
I wonder if the exhaust port on cyl #2 could use a little extra coolant as well?

Thom

FWIW I saw recently a full aluminium closed deck block based on a 3L block, with Nikasil cylinders. Perhaps a bit pricey to make but this should give less potentiel heat transfer issues than when pressing-in steel sleeves?

Yes but what's the point bumping up the knock threshold further when head lift/flex with E85 is already an issue with an 8V head...

333pg333

What boost are you hoping to run Sid?

67King

SEveral reasons. For one thing, not everyone has E85 at their disposal, and even when they do, it isn't always going to be available. Second, you can alleviate/eliminate that with O-rings. Third, the higher CR will give you more response/quicker spool. Fourth, significantly more power potential through more efficient combustion, and increased work from expansion. Fifth to to your point, your timing with a central plug will change, and because of the fact that the plug is in the middle, your MBT can occur later in the cycle, which will lower your peak cylinder pressure. It isn't average pressure that causes problems, it is peak. A central plug gives you higher average cylinder pressures with the same peak pressures.

The big reason to NOT go to a central plug is cost/simplicity. But for performance, it is better in every single way.

Sorry for the hijack, Sid. Wasn't trying to derail, but address the point about CR. By the way, I'm also not a fan of bigger bores, I much prefer the smaller bore/longer stroke way of doing it like you did. That changes when RPM becomes mechanically limited, rather than airflow limited.

blown 944

Tom, in all the engines I've done, I havnt seen any issues with the main bearings. So no need to do anything about the girdle IMO.

I thought about the larger studs. But tbh, I didn't have any issues with my head on the last engine. I'm probably not going to run much more boost than I did, so again no need IMO.

Like I said, I'm not looking for a lot more power than what I had.

Patrick, probably around 20-23 psi. I might try more and see how it goes, but probably not.

Harry, np. You must've mis read my new build. It is actually a bigger bore than what I had. It was the same price, so I went bigger. Eventually, I might go with a 95mm stroke too. Depends on how this one does.

Keeping the expectations lower now.

BC

On here? I need to find the article. I am speaking specifically of detonation and pre-ignition.

Of course one will see total peak cylinder pressure issues, but that is different - it is a controlled rise in pressure, and you can build a block around that.

Detonation is an uncontrolled explostion creating up to 10 times the "hp" or cylinder pressures a cylinder makes at its highest rated HP. A 400hp motor with 8 cylinders is making 50hp a cylinder in simple terms. A detonation event can cause it to see the cylinder pressure of 500hp, or 4000hp on the entire engine - not many are built for that.

BC

I have searched for quite some time. Can you point me where there is a tech article explaining where there was knock in an ethanol motor?

Yes, as mentioned, peak controlled ignition evens will have high pressures with high C/R and high boost. Is the motor able to withstand? You are suggesting the normal result of detonation - head lift and flex.

BC

I know you are an experienced engineer. I am a Technology guy. I research more than I have an ability to really test in the applied field.

I have not found anywhere discussing knock on ethanol.
e85 has a higher effective R+m/2 because of its cooling effect in pre-chamber and in-chamber. It is closer to 125 when used at its appropriate AFR (rich).
Peak Pressures will be from actual planned HP, and at that point, MY point is its a very different conversation.

The pressure has a different profile - it is not spiking and it is not acting against the mechanical direction of the piston.

refresh951

The thread I referenced was about cylinder pressure. As far as knock with E85 I really do not need an article as I have been running it for several years. I monitored knock closely and I can assure you it happens.

As far as cylinder pressure I believe the issue is more with the 8V head rather than the block. The bore size is large and the studs are a long ways apart. When you pull a head off you can see on a Cometic gasket that stuff is moving around significantly on a high power motor.

Here is my rational for going low CR on a boosted motor:

http://www.modularfords.com/threads/...boost-pressure

Rogue_Ant

A tech article? No, I haven't bothered to try and find any specific article. However, I have seen this many times.
If you really want a "source", try spending some time on the DSM forums - they are probably pushing the limits of E85 more than any other auto make.

As I mentioned before, at some point on the 951, peak cylinder pressures become high enough to lift/flex the cylinder head - even under normal combustion.

I wouldn't have bothered to mention the head lift/flex issue if it only existed for abnormal combustion events - as that isn't relevant.

67King

Sigh. There's a ton of misinformation out there. We used 108 when I was at Ford, Hot Rod is saying 105. http://www.hotrod.com/techarticles/h...l/viewall.html. As for the notion that it won't knock, given the right conditions, it will. Besides, continued increasing CR has diminishing returns. And on a 2V especially, the chamber shape can get really ugly, your surface area/volume ratio can get really unfavorable, and your thermal efficiency won't necessarily increase as it should.

On edit - Hot Rod differentiates between knock and pre-ignition. Knock really isn't a big deal, but it leads to PI, and PI is what breaks stuff. If E85 is more prone to PI, that makes it especially important you don't detonate, since the detonation creates hots spots, which cause PI.

333pg333

Harry, this is something I've been asking for years. I've always assumed knock and p.i. or what we call pinging are two different events. Assuming the P.I. is that rattle sound you hear on some cars running up a hill in a taller gear under load with low octane fuel. I have been informed that knock with E85 isn't really heard. It usually precedes a louder noise in quick succession which are engine parts separating.

67King

Patrick, not entirely sure. Knock is a generic term, but usually people mean detonation, where after the combustion process starts, the flame front's movement creates high pressure areas of unburned air/fuel on the perimeter. Once the pressure gets high enough, it just ignites (i.e. "detonates") from the pressure, like a diesel, but it is an explosion, which is the noise you hear. When I was doing calibration, we would put mics in the engine and hook them up to an oscillocope and headphones. You'd hear a little click, and when you'd hear them at a specific rate (e.g. one event every 5 seconds), you'd hold that base timing. So we never heard rattling, yet the engine did, indeed know. I've not worked with E85 in the vehicle, but the thermodynamics are the same, so I'd assume that the reasons it "isn't heard" are that the situation is compared to gasoline engines more closely tuned to their limits. A well tuned gasoline engine shouldn't really exhibit audible knock, either, but usually they get pushed in the aftermarket, so it can and does certainly happen. It is easier to build a gasoline engine close to that limit than it is an E85 one, as the piston shape becomes much more complicated......and it invariably has ridges and/or points where valve pockets are machined, which are VERY bad, and tend to like to serve as initiation points for PI.

PI is a result of detonation. Detonation creates hot spots, which then go on to act as ignition initiators. WHile you can retard timing (through the PCM) to get out of a knock situation, the ONLY way to stop PI is to cut fuel (i.e. the driver has to let his foot off of the pedal). And as not knock is going to be audible, having a fuel that is more prone to PI would be much riskier.

V2Rocket

Harry (and the rest of you kids),

give this a quick read, very interesting on the potential of the corn-juice.

http://www.nord-com.net/stoni/docs/SuTCAF.pdf

67King

SPencer, I scanned it (and I mean scanned), will read it thoroughly later. A few thoughts, Brake thermal efficiency isn't the same as fuel economy.......fuel economy actually goes down in terms of unit volume. I would be inclined to guess it would be an Atkinson engine, but I don't think you could make the chamber with late valve closing. It probably is the opposite, late valve opening, early valve events. So volumetric likely goes down, but the increased work from expansion (result of higher CR) makes it all work. So it really gets down to it being a system.

One of the cool things that has been done is a turbocharged, dual fuel, dual injection engine. RUns on gasoline via port injection under low loads, and E85 with direct injection under high loads. Made unbelievable torque.