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L28ET Street Car.. What size Turbo.....


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good info guys! I have a 76 280 and am planning to put a turbo on it too. My question is can I use the bottom end that is in the car now and put a p90 top end and turbo system on it? I know that the engine in it now is solid and thought it would be nice to keep it in there.

 

Just so you new guys understand, this website doesn't like to play 20 games with the 20 most answered questions, etc. They expect ya to search up and learn a bunch more in the process. Particularly since this is the turbo section.

 

Anyways, about the question of trim and A/R:

 

Trim: Gives you a designation of the nature of the wheel. You will have a trim number for both the turbine and compressor wheels. Generally this is what you tinker with a lot on the compressor side although there may be a few size options on the turbine wheel as well.

 

A/R: This number refers to the (essentially) constant ratio of the cross sectional area inside a slice of the turbine divided by the radius to the centerline of that slice. The larger the number, the tighter the "coil" of the turbine housing and the faster it will spool. The lower the number: the slower the turbine housing uncoils and the more friendly the turbine is to high flow (top-end). (think of it like large radius bends in piping versus tight bends). Generally this is what you tinker with a lot on the turbine side.

 

On the older Garret turbos, you will usually see T3/T4, etc. The first number (T3) refers to the size class of the turbine. The T4 refers to the size class of the cold side. When you see T04E, the E refers to the compressor cover's opening size. The E is a 3" inlet whereas the S is a 4" inlet.

 

Generally you can successfully vary the turbine A/R (ie., the turbine housing) along a couple choices and yield a few options with varying powerband characteristics for a particular engine and still be fairly effective for that car. In other words, assuming you have a good turbo configured for quick spool that has all the bits sized right to work together (and with the engine), you can change up the turbine housing to the next size down in A/R and have good mid/top end(-ish) turbo that is still working together pretty well. This makes for a cheap and easy way to "change your mind" or reconfigure the turbo. On the other hand, the compressor and turbine wheels are built as part of the CHRA (center housing rotating assembly) and changing a wheel requires the CHRA to be rebalanced (much like changing to different pistons on a rotating assembly).

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Just so you new guys understand, this website doesn't like to play 20 games with the 20 most answered questions, etc. They expect ya to search up and learn a bunch more in the process. Particularly since this is the turbo section.

 

Anyways, about the question of trim and A/R:

 

Trim: Gives you a designation of the nature of the wheel. You will have a trim number for both the turbine and compressor wheels. Generally this is what you tinker with a lot on the compressor side although there may be a few size options on the turbine wheel as well.

 

A/R: This number refers to the (essentially) constant ratio of the cross sectional area inside a slice of the turbine divided by the radius to the centerline of that slice. The larger the number, the tighter the "coil" of the turbine housing and the faster it will spool. The lower the number: the slower the turbine housing uncoils and the more friendly the turbine is to high flow (top-end). (think of it like large radius bends in piping versus tight bends). Generally this is what you tinker with a lot on the turbine side.

 

On the older Garret turbos, you will usually see T3/T4, etc. The first number (T3) refers to the size class of the turbine. The T4 refers to the size class of the cold side. When you see T04E, the E refers to the compressor cover's opening size. The E is a 3" inlet whereas the S is a 4" inlet.

 

Generally you can successfully vary the turbine A/R (ie., the turbine housing) along a couple choices and yield a few options with varying powerband characteristics for a particular engine and still be fairly effective for that car. In other words, assuming you have a good turbo configured for quick spool that has all the bits sized right to work together (and with the engine), you can change up the turbine housing to the next size down in A/R and have good mid/top end(-ish) turbo that is still working together pretty well. This makes for a cheap and easy way to "change your mind" or reconfigure the turbo. On the other hand, the compressor and turbine wheels are built as part of the CHRA (center housing rotating assembly) and changing a wheel requires the CHRA to be rebalanced (much like changing to different pistons on a rotating assembly).

 

 

great.. thanks alot.. very informative... i tried looking at garrets page.. but couldn't find that nfo..

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please nobody tell him and make him go search for the answer!!!!

 

 

I did search on here and on internet.. i have seen posts talking about p90's pairing it on various heads and modifying them.. i have seen posts about people looking for a specific year p90 head.. based off that it looks like the 83's have that head..

 

but didn't see a break down of what years came w/ the P90 head on the L28ET

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All year L28ET came with P90 heads. Some 1983 L28ET came with P90a heads, which have hydraulic lifters instead of solid lifters.

 

You really do need to search a little harder as I KNOW the info is out there and easily found. I would highly recommend checking out all the stickies in all the forums that are interesting to you. most of what you have asked can be found in these posts. It takes a little more time on your part, but it really is frustrating to see the same questions asked over and over again.

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All year L28ET came with P90 heads.

 

Don't think that's true; if I understand what you're trying to say.

 

Check here and expand out to the root website for a boatload more info. I recommend you start a new section in your browser and organize all the places you find info with bookmarks.

 

http://www.atlanticz.ca/zclub/techtips/cam/index.htm

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