Gt 4088 vs gt 4094 R

[Grant Monkhouse]

I am asking for peoples advice between these turbos as I worked out how much a full setup would cost, turbo, wastegate, BOV, electronic boost controller. With a normal turbo the price is a he\'ll of a lot cheaper and I can\'t see a bb turbo giving me a huge amount more power?

Obviously the compressor wheel is bigger but maybe I can get hold of a journal bearing 4094?

I don\'t think I have come across one of these yet?

[Nik da Greek]

As on the ball bearing turbos being a no no on rotaries I think is rubbish. How hot is it actually going to get when it is water cooled?

Is that a trick question! Hot enough for the compressor housing to glow red :3Confused I agree though, I think the myth of rotaries killling ball bearing turbos is probably at best exaggerated and at worst utter hogwash. Probably comes from a few drag racing failures where the stresses are extreme and as usual with the intranerd has been taken and ran with. Mind you, what do I know hahaha :Giggle

[Grant Monkhouse]

Is that a trick question! Hot enough for the compressor housing to glow red :3Confused I agree though, I think the myth of rotaries killling ball bearing turbos is probably at best exaggerated and at worst utter hogwash. Probably comes from a few drag racing failures where the stresses are extreme and as usual with the intranerd has been taken and ran with. Mind you, what do I know hahaha :Giggle

Wheni said how hot will it get I meant the bearing, as with the water taking the heat away? I think that if a bb turbo was to fail then that would be due to other components, online oil filter, blocked water feed etc, the same as having a rubbish intercooler and a radiator on your rotary?

Bb turbos are new turbo technology whereas journal bearings have been around for donkeys years, but I am trying to justify how much to spend on one of these things as 1200 quid on a lump of metal that might fail due to "heat" :3Confused is a lot of money?

[scratchies]

i have gt4094r and the turbo has run very well indeed made 437 @rwhp and gave me full boost 1.3 by 4000 rpm and make power right up to 8000 ish revs  positive boost by 3200 have run this in the car for 2 and half years so its is very good turbo BUT as of last week it has sarted to smoke small amount sometime at idle but still pulls like a train for the money they are very good but to buy parts ect they are bad like cores £1000 not repairable funny that you may just go buy new turbo if you no what im saying but over all there not bad just alot to buy and replace
 
 

Wheni said how hot will it get I meant the bearing, as with the water taking the heat away? I think that if a bb turbo was to fail then that would be due to other components, online oil filter, blocked water feed etc, the same as having a rubbish intercooler and a radiator on your rotary?
 
Bb turbos are new turbo technology whereas journal bearings have been around for donkeys years, but I am trying to justify how much to spend on one of these things as 1200 quid on a lump of metal that might fail due to "heat" :3Confused is a lot of money?

[turbotoaster]

i wouldnt bother with a rollerbearing turbo at all, they cost twice the price most of the time, they are weaker as remember rotarys have higher EGT temps than piston engines, which can cause you to cook the shafts, also if a roller does go most of the time you will have to replace the core with costs nearly the price of a new turbo anyway.


the gt4094 will make more power because of its larger comp wheel but depending on how much power you want depends on what turbo you need.

For example on a big streetport a gt4088 will do 480bhp @1bar and 525bhp@1.2bar, then if you want more power than that then you can turn the boost up with water.

If you want more than that at either low or high boost then like scratchies says the gt4094 is a good turbo, my concern would be to make sure you get a decent sized turbine housing as the turbine wheel is quiet small compared to the compresser so it will help with pre-turbine back pressure.

If i was looking at gt4094 to be fair id just get a gt4294 and be done with it, as that has a better turbine/comp ratio, but thats just me.

the GTX serious are great turbos but very expensive and only really come into there own at higher boost pressures, only really then you can justify there costs

Infact id choose a borgwarner over a garrett because they are so cheap yet make power, ive seen results of outspooling a garrett with similar wheel sizes aswell.

BOV arnt really needed, yes they can help transision when coming on and off the throttle because they help against the slowing down of the wheels but you can run without on.


if you want impartial advice send me an email on turbo-toaster@hotmail.co.uk and ill run you through some ideas, after which you can ask people on here what they think of my ideas:Giggle

[Grant Monkhouse]

i have gt4094r and the turbo has run very well indeed made 437 @rwhp and gave me full boost 1.3 by 4000 rpm and make power right up to 8000 ish revs  positive boost by 3200 have run this in the car for 2 and half years so its is very good turbo BUT as of last week it has sarted to smoke small amount sometime at idle but still pulls like a train for the money they are very good but to buy parts ect they are bad like cores £1000 not repairable funny that you may just go buy new turbo if you no what im saying but over all there not bad just alot to buy and replace

That is bad news to hear about your turbo, do you think that the core has actually messed up or possibly your oil feed is that tiny little bit too big as I know the hole has to be small as the oil required is much.

[Grant Monkhouse]

Turbotoaster. I was wondering about the size of the hotside, As obviously the bigger it is the later the spool up? And the higher up the rev range is where the power would be? Am I thinking on the right lines there? Tell me if I\'m not so I learn. Also the bigger the hot side the faster the heat goes away from the engine, keeping air temperatures that bit lower, in turn helping produce more power? Due to more oxygen in the air?

If I wanted the power from 4,000 to 8,000 rpm would a 1.06 hotside be about the right size or too small?

[HaywardRotary]

Grant,
Ball bearing turbo\'s are fine.
The GT35r series have plastic casings holding the bearings,GT40 range has brass.
Water cooling keeps them both safe,they spool earlier than plain bearings which is their main advantage.
If you are not worried about that then go for plain bearings.My current turbo of choice is GT40/94
Regards
Carl

[Grant Monkhouse]

Grant,
Ball bearing turbo\'s are fine.
The GT35r series have plastic casings holding the bearings,GT40 range has brass.
Water cooling keeps them both safe,they spool earlier than plain bearings which is their main advantage.
If you are not worried about that then go for plain bearings.My current turbo of choice is GT40/94
Regards
Carl

I\'m not worried about the myth of the rotary being too hot for the turbo, I\'m just thinking of the price difference for the performance gained really, as for the 40/94 being twice the price would I feel the benefit of twice the performance? I could buy two journal bearing turbos for the price of the one?

If my car was mapped up to 1 bar with either of these turbos, what would be the difference in hp and delivery?

Just trying to learn a bit more in turbos as there are only so many books I can read before they all start sounding the same, lol. I think I have read 3 or 4 and they say similar things but in different words.

[HaywardRotary]

About 1000 rpm in responsiveness but top end power the same.
Regards
Carl

[turbotoaster]

Turbotoaster. I was wondering about the size of the hotside, As obviously the bigger it is the later the spool up? And the higher up the rev range is where the power would be? Am I thinking on the right lines there? Tell me if I\'m not so I learn. Also the bigger the hot side the faster the heat goes away from the engine, keeping air temperatures that bit lower, in turn helping produce more power? Due to more oxygen in the air?

If I wanted the power from 4,000 to 8,000 rpm would a 1.06 hotside be about the right size or too small?

Your very close, its normally ideal to get an equal turbine to compressor wheel size when you get a turbo for a rotary, that you get a good balance between \'pushing air in, and letting air out\'.

Since 99.9% of turbos werent designed for rotarys but pistons engines then its a bit of a compromise, normally this does make a massive difference until you turn the boost up, at which point it comes into effect.

By going for a larger turbine housing you decrease the restriction because less of the exhaust gas is being blown over the turbine wheel(its just being let out into the exhaust) by having less of a restriction, more gas can be pushed out and in turn because its easier to get the gas out of the engine, its also easier to get gas into the engine.

This improves the VE of the engine....bit like when you but a bigger exhaust on a car, less restriction so you make more power.

The issue with a larger turbine housing is that because theres less air blowing on the turbine wheel, it takes longer to spool.

Its not that your maxpower will be later in the rpm range normally, but that the power will not drop off as much at very high rpm, but then it depends what rpm you will finally rev to.

To decide what turbo is right for you we need to ask a few questions.


The most important is what power do you actually want, when its all mapped and you get given a dyno sheet, what number will actually make you happy?

Then we need to know what boost level will you be comfortable running, id imagine your gonna run w/i, so is 1bar max, 1.1, 1.2,1.3,1.4+ that bit is down to yourself, yes more boost will normally equal more power but as the boost increases you will need someone who is good with mapping at that sort of power, id say dragfon, reworx or Jaydee would be my choices.

you mention 1.06, that might be fine, it might be not, it all depends on how much boost you wanna run and your final power.

say you had a certain power goal, there are 2 ways to skin this cat.

You can either use a big turbo which means you will loose response and spool later but you will only have to run a very low amount of boost to hit your target power.

or

You  can use a smaller turbo which means you have better response and earlier spool but you will have to run a bit more boost to which means your mapper has to be better and you have w/i to hit your target power.

I\'m not worried about the myth of the rotary being too hot for the turbo, I\'m just thinking of the price difference for the performance gained really, as for the 40/94 being twice the price would I feel the benefit of twice the performance? I could buy two journal bearing turbos for the price of the one?

If my car was mapped up to 1 bar with either of these turbos, what would be the difference in hp and delivery?

Just trying to learn a bit more in turbos as there are only so many books I can read before they all start sounding the same, lol. I think I have read 3 or 4 and they say similar things but in different words.

going to a ball bearing doesnt give you twice the performance, on a piston engine i would recommend one is your feeling rich but on a rotary i just see it as to much risk.

piston engines can go up to 800c under full WOT flat out, ive seen people do 900c lean cruising with a rotary, its not that the temps are massively different, its just that rotary puts hot gas out all the time compared to a piston engine.

like i say, tell me what power you want, your budget and see can see what we can come up with:yes