Strength of the 2.0L - Alfa Romeo Bulletin Board & Forums
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post #1 of 8 (permalink) Old 06-02-2019, 08:52 PM Thread Starter
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Strength of the 2.0L

As I continue with the modifications on my Turbo 2.0 Spider, I find myself wondering what the weak link is in this motor. I’m currently pushing 207hp at the wheels (~240bhp) on 93 octane and 14psi of boost. I will soon switch to e85 and tune it to suit, where I will likely see even more gains from additional timing. The engine is bone stock from valve cover to oil pan with 113k miles, though it is unknown whether or not it has been rebuilt by a previous owner. So my question is, where’s the limit? What’s the weak link? Headgasket? Rods? Pistons? I will build a motor in the future, but for now the stock motor is holding just fine, and is reliable enough to be my daily driver with the occasional long trip.
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1987 Spider
Stock Engine, Turbocharged, Megasquirt MS3x, Flex Fuel - 207whp
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post #2 of 8 (permalink) Old 06-03-2019, 12:35 AM
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Headgasket, due to open block design permitting the liners to move when under huge pressure
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post #3 of 8 (permalink) Old 06-03-2019, 05:42 AM
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208WHP is the abso-lute limit! hahaha

I am not sure anyone has scientifically found the limit of a stock motor but something tells me you are about to! Head-gasket would be my first guess. Rods are probably fine over 300BHP in short bursts and I assume your redline is relatively tame. As long as you have fuel and spark well managed with some safety protection for knock and overboost you should be fine. You have an aftermarket radiator so I will assume you have the added thermal load managed too. While a turbo does add to total cylinder pressure the "secret" to turbo power is the increase in CP is not that much, it just lasts longer through the combustion stroke.

Do you have a dyno chart?

-Brian
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post #4 of 8 (permalink) Old 06-03-2019, 07:00 AM
Richard Jemison
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Old Stock Engine Boosted??

Just my $.02 worth:

Brian`s right on "Limits" for the 2 liter, but with an old 113K mile motor you should expect failures as common "performance" built engines have improvements to the stock components to improve life.

From your post I "assume" the liners are not grooved ( that or "o-ringed") to lock the fire ring in place. Migrating o-rings with high combustion pressures is common. Torquing the head to 75 lbft will help prevent this.

Just from the pics of the aluminum radiator I suspect it is sorely undersized for this application.

Rj

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post #5 of 8 (permalink) Old 06-03-2019, 07:27 AM Thread Starter
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Quote:
Originally Posted by 4SFED4 View Post
208WHP is the abso-lute limit! hahaha

I am not sure anyone has scientifically found the limit of a stock motor but something tells me you are about to! Head-gasket would be my first guess. Rods are probably fine over 300BHP in short bursts and I assume your redline is relatively tame. As long as you have fuel and spark well managed with some safety protection for knock and overboost you should be fine. You have an aftermarket radiator so I will assume you have the added thermal load managed too. While a turbo does add to total cylinder pressure the "secret" to turbo power is the increase in CP is not that much, it just lasts longer through the combustion stroke.

Do you have a dyno chart?

-Brian
I’ll have to search for the dyno chart, but I uploaded a video I had on my phone of the run, showing some early dyno pulls as I was dialing in the boost control prior to finalizing the ignition map. The most I hit was 18psi, but I felt that was going to be pushing it when I added timing.

https://youtu.be/TtLEpPfgox0

Rev limit is 7k with a 200rpm soft limit
I have overboost protection at 18psi
No knock sensors

1987 Spider
Stock Engine, Turbocharged, Megasquirt MS3x, Flex Fuel - 207whp
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post #6 of 8 (permalink) Old 06-03-2019, 07:46 AM Thread Starter
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Originally Posted by Alfar7 View Post
Just my $.02 worth:

Brian`s right on "Limits" for the 2 liter, but with an old 113K mile motor you should expect failures as common "performance" built engines have improvements to the stock components to improve life.

From your post I "assume" the liners are not grooved ( that or "o-ringed") to lock the fire ring in place. Migrating o-rings with high combustion pressures is common. Torquing the head to 75 lbft will help prevent this.

Just from the pics of the aluminum radiator I suspect it is sorely undersized for this application.

Rj
Failure is always an option. I know it’s risky to run an old motor this hard. I have not done anything internal to the engine. I have another engine sitting around ready to be built. Has anyone made a closed deck Alfa motor? There are deck plates on the market for other applications, but none for anything with floating sleeves, at least that I know of.
Before I tune on e85, I will retorque the head studs to 75ft lbs one at a time.

1987 Spider
Stock Engine, Turbocharged, Megasquirt MS3x, Flex Fuel - 207whp
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post #7 of 8 (permalink) Old 06-03-2019, 10:46 AM
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Your pinion bearing will not like you for long! No closed deck solutions on the market, you can make your own mono-liner but that is a costly endeavor. Some Honda and Mitsu guys fill the water passages with cement the block for strength. Glue your liners in to the block, that will add rigidity and 0-ring your liners to the head and that will help control head gasket failures. The Reinz HG is very reliable in this configuration.
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post #8 of 8 (permalink) Old 06-03-2019, 11:01 AM
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I think you are probably at about the limit of the stock motor, but so much depends on use. A car that could be dead nuts reliable for 10s of thousands of miles for the occasional hard pull on the street might not make it through a 20 minute track session.

The failure point for me was head gasket. It was set for 7psi, though it was over-boosting a bit due to cold temps- data logs show it was at 9psi. Mind you, I abused the snot out of the motor for a few years prior, and it bounced off the rev limiter for several seconds prior (autocross run with no time to shift).

I'm going with the O-ring method for version 2.0, along with forged pistons/rods, and stronger liners. I'm not sold on epoxy for the liners, but I suppose I will consider it if version 2.0 blows. I'm planing on at least doing a tune for 300whp for that one, though I will probably turn down the wick for track days.

Others are right that the open deck is the biggest limitation. A deck plate to convert it to a semi closed deck could probably rectify the situation cheaper than a monoliner. But if you aren't doing Bonneville top speed runs or 24 hour endurance races, I think you are overwhelming the chassis at power levels below where a monoliner becomes necessary. Any solution will require custom work. Unfortunately, our Alfas aren't like tuner cars where 1,000whp+ capable billet blocks can be ordered off the shelf.

Last edited by nealric; 06-03-2019 at 11:07 AM.
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