GT25 Turbo suitability
Turbo Mini Forums

Thought i'd let you all know this.

Had quite a chat with my turbo builders at Autosport yesterday and we got onto chatting about the newer spec units. Basically you can forget about the GT25 as its way out of map for our use. He did say that he could play around with them, using some special housings he has made, but even then he didn't think it would be much cop.

That leaves us with the GT20 and smaller units. These can be built to our needs, but are not available with ball bearing centre housing !!

Oh and turbos from diesels are not good for petrol engines. The materials used in both the housing and turbine are different and will degrade when used in petrol application. He said it is not uncommeon for the turbine rotor tips to melt and the housings cracking.

interesting stuff, poor show from Garrett as their catalogue quotes the GT25R as being suitable for 1.4L upwards

i'm reckoning on the GT15 being next best, might not be ball bearing, but uses later technology for all the design etc. Plus you can get it with a T2 exhaust inlet flange

the housings on diesel turbos are identical......

and if turbos for diesel are not suitable for use on petrol engines, why do they list the powere made in each sore of engine for each turbo on the garret website....... i understand there may be one or two very specific turbos designed specially for diesels but most are designed with either use in mind......

pete

And on the 7th day........... God created turbochargers!

Yeah we figured out last week (via TD) that the gt25 was too big. A/R's all start too high.

GT15 looks like the business though.

To clarify a couple of the points you guys say.

They can be suitable for a 1.4 engine, just not one putting out say 140 bhp. It's not justy down to engine capacity, it's the output from the engine. More power equals more fuel burnt and more air needed to burn it at correct ratio. Look at the turbos on the old 1.5 ltr F1 cars from the 80's, these are more like truck turbos, huge lag but huge power potential when you can get them spinning (upto 1400 bhp in qualifying).

The housing is identical. Well it may look the same and may have come out of the same mould, but may be cast from a different spec material. As a volume manufacturer garrett will produce the units as cheaply as they can to meet required spec and if they can save ?0.50 on each casting they will. If they sell 1000.000 a year thats a fair saving. And its not just cost of materials, its the machining cost, better materials can need better tooling to machine them or just wear out tools quicker or may take longer to machine as the materials cutting speed is lower, so it all reflects in the cost. So if they can shave a small amount of each unit they will. Same thing goes for the turbines materials, why make it good for higher temps when its only going to see lower ones in its life fitted to an oil burner.

They quote power figures for each fuel type as they supply turbos (be it gt15, 20, 25, etc) to suit both fuel types. But the units are not the same.

Its like buying photoshop for your pc and expecting it to run on Mac, same product made different.

Got to admit im kinda suprised that they do not do a really good spec smaller unit for the hot hatch type of sector, guess the market is not there or they would.

Rich,
Is the Material the 'PT' number on the castings then?
I've noticed PT-1 PT2 and PT4 on different (seemingly identical) housings, just near where the A/R number is on the outer part near the flange on the T2 range...

I'm not surprised that a GT25 'off the shelf' doesn't suit out motors, but I'm sure some GT 'parts' (compressor&housing for example) would be suitable - how much of a gain I've no idea!!!!

To be honest dave im not 100% sure, but i'll check it out and see what i can tern up. I mean those figures mean nothing to me as far as a material spec, so i guess it must be an inhouse label.

sorry does this mean all t2.5's are out of the question, just asking as i was hoping of using a turbo in beyween a t2 and t3, if i get an uprated t3 ball bearing 360 etc will this significantly reduce lag?

PT1,2,3,4 or sometimes M1.2.3.4 are the material specs of the turbine hsg, it represent the part of maganese used in the cast iron , it's why it can take so much temps, the higher number is the best, and they are more safe to cracks, and as with all the T2's it's not a question of turbo or not, I've seen different numbers from td or petrol engines without any reason (even with the same casting and part number),
about the gt serie I can't tel about them, as I don't know them enoughly, but they are more efficient and worth an headacke , specialy the vnt 15/17 series .
fab

Gav in answer the your question T25's are perfectly suitable - the GT25 is different turbo completely

cheers thats exactly what i wanted to here