Engine comparison 2.3T vs 2.5T Topic is solved

madsking · Post by **madsking** » 19 Aug 2020, 23:58

Good day to you

The other day I saw something that I did not think was possible so now I would like to understand how.

I bought a Volvo 850 T5 (2.3) from a guy I know well because I needed the engine for my own project car. The T5 was driving really good and pulling like crazy so that engine was kind of approved

Besides that it also has a very low mileage.

Anyway when I unmounted the engine I discovered that the engine was a 2.5 instead of the expexted 2.3! Obviously it has been replaced at some point back in time BUT the very interesting part is that the ECU was the 2.3

Sensors and stuff like that I see is the same on the outside but still, how about ignition points, compression, volume and all of that.. how can this ECU work together with the 2.5 ?
Hope somebody can clear that out for me

Perhaps I should consider actually using the 2.5 instead if it can give me more power just like that, plug and play..

Thank you

Pasting few images as well

I did control the engine code on the block itself and it does say B5254T

madsking · Post by **madsking** » 20 Aug 2020, 04:31

I have found that the cylinder stroke is the same for both engines (90mm) which can be the magic reason?

callahanoffroad · Post by **callahanoffroad** » 20 Aug 2020, 05:54

So we call that the 2.4 low pressure turbo here in the US. The 2.5T is the later low pressure turbo used in the s60 etc.

The biggest difference between your current engine and the original engine is slightly higher compression 9.6 vs 8.5 IIRC, and slightly larger pistons 81mm vs 83mm IIRC.

Someone probably just pulled the engine, swapped the intake, exhaust, turbo and injectors and popped it back in there.

There's no reason a LPT engine can't handle the engine mapping of a HPT or R ECU.

Alternatively your car is actually a LPT from the factory with an R ECU.

Check out the injectors, VIN plate, and turbo to confirm what happened.

Hope that helps. I haven't had enough coffee yet.

Post by **Chuck W** » 20 Aug 2020, 06:26

It is possible an LPT motor was swapped in at some point in the car's history. The compression difference, (9:1 vs 8.5:1) isn't all that much, and as stated, it would probably run mostly OK on the T5-R ECU.

However...Looking at that "SAM" sticker on the ECU and a quick Google shows that *may* be a tuned or chipped ECU (Sam Steffansen), but it doesn't look like he's active any longer. Opening up the ECU would show if it's been altered in any way.

We ran the wife's '97 LPT car on a couple HPT ECUs while sorting out some tuning/AC details (Specific to the '97 LPT cars) and they would run OK, but at higher boost, we'd see some detonation. More than likely due to the more aggressive timing maps for the HPT tunes at higher boost. We have a tunable/flashable one in there now, so the point is irrelevant now.

Personally, I would stick with the LPT motor for the higher static compression for a car that is more of a driver.

madsking · Post by **madsking** » 20 Aug 2020, 07:26

Thanks both of you, it's always a pleasure reading the feedback.

I spoke to the owner of the car who confirms engine has been replaced at a workshop few years ago after drop of oil, though he was not aware that it was swapped to a different type, especially not due to the power of the engine didn't drop at all but more the opposite after the swap. I also drove it myself before taking engine out and confirm that it pulls like crazy.

Looking at the engine picture it's also visible that the injectors are red which are the stock ones for the 2.5T

"SAM" was the Volvo team that tuned the 850 for the race track back in the 1990's and can be considered as the former Polestar

Simply I wouldn't believe that 2.3 ECU would work on a 2.5 with the different piston size and compression but you have learned me that now and I kind of found new opportunities as the 2.3 engine is hard to find anymore.

/ Mads

Post by **Chuck W** » 20 Aug 2020, 07:30

I would still open that ECU (Pretty easy to do) and see if any non-stock items are in there.

madsking · Post by **madsking** » 20 Aug 2020, 08:30

I did that with another SAM ECU once and the original chip is replaced with a socket where the tuning chip is mounted. That's basically what SAM was doing as a business back then. Attaching a picture.

callahanoffroad · Post by **callahanoffroad** » 20 Aug 2020, 20:01

Very cool

madsking · Post by **madsking** » 21 Aug 2020, 00:01

Interesting how much horsepower this thing was supposed to have when it was installed back in the days