Gt 35/40 turbo ??
30-10-2005, 09:52 PM
#1
Gt 35/40 turbo ??
Hi Peeps
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
30-10-2005, 11:14 PM
#4
Norris Motorsport
On a 2.0 YB the surge issues with GT35's can be improved with the correct selection in cams and the use of a suitable tubular manifold and large throttle body. However after having mapped around 15 engines with GT35's (May I add most NOT built by myself) all surge to some degree. The worst spec engines surge all the time with any boost over 26psi up to 5500rpm, where as the best spec engines only surge when running max boost at part throttle up to 5500rpm. Either way they're a surgetastic turbo!!! 
30-10-2005, 11:24 PM
#5
DEYTUKURJERBS
i dont really unerstand the question, but a GT35/40 is just another term for GT35s that most people use TBH, as they have a GT40 compressor.
Kinda like RS500 turbos have a T4 compressor but not a T4 turbine side.
Why do 2litre YBs surge with GT35s and so many other 2litres etc dont then?
Kinda like RS500 turbos have a T4 compressor but not a T4 turbine side.
Why do 2litre YBs surge with GT35s and so many other 2litres etc dont then?
30-10-2005, 11:29 PM
#6
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Can I just ask as well. Karl? What is surge? 
and how bad is it to have it?
lookin at a gt35 on a 2litre engine
should I really avoid it?
Thanks
and how bad is it to have it? lookin at a gt35 on a 2litre engine
should I really avoid it?
Thanks
30-10-2005, 11:31 PM
#7
Norris Motorsport
Steve, the issue with GT35's surging is related to the YB efficiency. The YB seems to improve considerably in its VE over 5500rpm and as such below 5500 is the surge zone when using a GT35. If you also look at the compressor map for the GT35r you will see that at pressure ratios over 1.6 bar the surge line is rather shit!! As such it is not uncommon to have to cap 2.0YB's to around 25psi until after 5500rpm.
As I've mentioned above this situation can be improved with other parts, but Ive yet to see an engine spec that has no surge at all with a GT35r as even the best ones still surge when running full boost at part throttle under 5500rpm.
I'm looking forward to a ride in Ade's car at full boost and part throttle as Rod says it has no surge at all!!!
As I've mentioned above this situation can be improved with other parts, but Ive yet to see an engine spec that has no surge at all with a GT35r as even the best ones still surge when running full boost at part throttle under 5500rpm.
I'm looking forward to a ride in Ade's car at full boost and part throttle as Rod says it has no surge at all!!!
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31-10-2005, 01:41 AM
#10
GT35/40 is a pretty vague description too, there a fair few configurations possible.
Trouble is that things that you do to minimise lag generally, like a smaller exhaust housing increase the chance of surge.
Still possible to get good results from them on a high revving motor though.
If you are building to 8500rpm anyway then reasonable power from 4000 and monster power from 5500rpm is a not bad bet, so even working around the surge you can still make a very quick car, but for a road going car i would sooner have a GT30R really myself on a YB, so i reckon you would be best to swap it if you do get it.
Trouble is that things that you do to minimise lag generally, like a smaller exhaust housing increase the chance of surge.
Still possible to get good results from them on a high revving motor though.
If you are building to 8500rpm anyway then reasonable power from 4000 and monster power from 5500rpm is a not bad bet, so even working around the surge you can still make a very quick car, but for a road going car i would sooner have a GT30R really myself on a YB, so i reckon you would be best to swap it if you do get it.
31-10-2005, 06:54 AM
#11
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Originally Posted by chip-3door
GT35/40 is a pretty vague description too, there a fair few configurations possible.
Trouble is that things that you do to minimise lag generally, like a smaller exhaust housing increase the chance of surge.
Still possible to get good results from them on a high revving motor though.
If you are building to 8500rpm anyway then reasonable power from 4000 and monster power from 5500rpm is a not bad bet, so even working around the surge you can still make a very quick car, but for a road going car i would sooner have a GT30R really myself on a YB, so i reckon you would be best to swap it if you do get it.
Trouble is that things that you do to minimise lag generally, like a smaller exhaust housing increase the chance of surge.
Still possible to get good results from them on a high revving motor though.
If you are building to 8500rpm anyway then reasonable power from 4000 and monster power from 5500rpm is a not bad bet, so even working around the surge you can still make a very quick car, but for a road going car i would sooner have a GT30R really myself on a YB, so i reckon you would be best to swap it if you do get it.
31-10-2005, 07:05 AM
#12
Marco - personally i would go with a decent t4 - rev limit to 7800/8000 and a pair of karl's cams, a new inlet - either an nms item or the swedish one. And some 1000cc injectors 
MUCH less hassle and all you need is a turbo/cams/inlet/injectors and a remap...
Your noise will not be as much of an issue and you don't have to have all the noise of a screamer.
MUCH less hassle and all you need is a turbo/cams/inlet/injectors and a remap...
Your noise will not be as much of an issue and you don't have to have all the noise of a screamer.
31-10-2005, 12:05 PM
#16
For all those people who think a GT35 Surges on a 2Litre, i believe Ades car will be proving differently on Thursday at the Daddy Thrash.
Martin & Karl have been invited to attend i believe they have excepted. That will put an end to these type of posts. If the Engine/Head/Cams are correct THEY DONT SURGE.
Rod
ps. Getting Blue in the face saying this.
pps. Marco Perhaps you are asking the wrong people & if you wish to fit this Turbo you should know by now who to ask.
Martin & Karl have been invited to attend i believe they have excepted. That will put an end to these type of posts. If the Engine/Head/Cams are correct THEY DONT SURGE.
Rod
ps. Getting Blue in the face saying this.
pps. Marco Perhaps you are asking the wrong people & if you wish to fit this Turbo you should know by now who to ask.
31-10-2005, 01:28 PM
#17
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No idea about these turbos on YB's but... As chip said - Gt35/40 is a useless description, it only tells u that it has a 68mm turbine inducer. So unless you know the compressor details, u cant look at a map to see if it's going to work!
31-10-2005, 01:35 PM
#19
Basically what you are saying is like saying "ive been told esorts arent any good for rallying, im getting one cheap, should i use it or swap to a sierra"
But at no point mentioning if its a WRC escort cossie, or a 1.1 popular plus.
But at no point mentioning if its a WRC escort cossie, or a 1.1 popular plus.
31-10-2005, 01:36 PM
#20
Originally Posted by Rick
Don;t know about surge, but here'e a proper 500hp turbo, unlike the T4 being more of a 440hp turbo - GT3076R
T4 just will not surge no matter what you to do it basically!
Lot to be said for reliable old technology sometimes!
31-10-2005, 02:30 PM
#22
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Marco im currently stuck with the same dilema, have gathered most my parts for a rebuilds but unsure what to use. Shall be speaking to Reyland in regard to rebuild and spec etc.
The turbos pictured are gt28/35 and gt35/40. Also hks external wastegate
May have to sell one or the other depending on outcome.
The turbos pictured are gt28/35 and gt35/40. Also hks external wastegate
May have to sell one or the other depending on outcome.
31-10-2005, 02:59 PM
#23
Originally Posted by SapphyMike
A T4 can surge Chip.
As Stu once put it, a T4 is the mayor of Surgeville, or something like.
As Stu once put it, a T4 is the mayor of Surgeville, or something like.
Get the correct T4 and it wont surge, even if you make bad choices on cams and headwork etc, a GT35 though, seems to be VERY fussy about all aspects of the engine to avoid surge.
31-10-2005, 03:21 PM
#25
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Dom,
an the most hated of phrases, surge sounds like "wastegate chatter", in that instead of getting it when you let off the throttle, the "chatter" is there under load.
the engine cant consume the air that the turbo is pushing quick enough, hence the noise iirc. I think, but trust me, i'm probably wrong, that the turbo is also trying to stall too.
Remember tho, wastegate chatter doesnt exist, and its turbo stall - happy Rainbum? LOL
Its bad cos it can fuck your turbo iirc LOL
an the most hated of phrases, surge sounds like "wastegate chatter", in that instead of getting it when you let off the throttle, the "chatter" is there under load.
the engine cant consume the air that the turbo is pushing quick enough, hence the noise iirc. I think, but trust me, i'm probably wrong, that the turbo is also trying to stall too.
Remember tho, wastegate chatter doesnt exist, and its turbo stall - happy Rainbum? LOL
Its bad cos it can fuck your turbo iirc LOL
31-10-2005, 04:31 PM
#31
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Originally Posted by dingy
T4 is only a 440bhp turbo - afpmsl....
mine made more power than that with out being remotely close to its limit
mine made more power than that with out being remotely close to its limit
31-10-2005, 04:53 PM
#32
T4 just will not surge no matter what you to do it basically
They surge mate been there...even on a lightly ported head above 25psi and its a nightmare....open ports right out and use correct cams then its fine just like the GT35
Also to Rick a T4 is a genuine 500bhp turbo..providing you have a good spec engine @ 2bar boost..reliable all day everyday
31-10-2005, 04:59 PM
#33
T4:
After around 440bhp a T4 is a restrictor. We can push the air harder and harder and make more power, whilst generating more heat, but we are fighting the turbo itself and would be better fitting a bigger more suited turbo, end of story. Peeps in the Ford scene would do well to remember that having to use 2bar of boost is not actually a good thing
Surge:
Surge is caused by the stall, which is worsened by surge, its a vicious circle... 
Imagine the way our turbocharger's compressor is driven, right back to basics: The turbine wheel is spun by exhaust gas, utilising also the energy stored in the exhaust gas as latent heat.
This force on the turbine shaft generates torque at the compressor end as they are physically connected. Remember that part as its the key element, Torque
Ok,
Now lets imagine our turbocharger compressing air, forcing it into the engine, the engine is utilising it.. what happens then? Ok, The engine expells it, and our turbine housing pressure goes up accordingly, the torque applied at the turbine wheel increases, increasing the spin speed and compressor efficiency at the other end. Great chain of events!
End Result? boost is climbing nicely.
Ok,
Now imagine this scenario:
The turbo begins to spin, as above, but the compressor wheel is generating more air than we can move and the torque required to spin that huge compressor is not being met? Remember that unless the air is processed by the engine, and expelled as hot, rapidly moving air into the turbine housing, our turbine shaft torque will not increase to spin the compressor faster, and it may well diminish.. our compressor is slowing, braked massively by the compressed air its trying to overcome and increase.....
Result? Compressor starts to slow a little.. (beginings of a compressor stall)
Ok,
So now what?
The engine is still rotating and consuming air, but the turbo has stopped producing an excess, so our engine has now had chance to consume what excess was available and the inlet pressure is now diminishing, the turbine torque is now increasing again...
VERY IMPORTANT:
Remember also that at same time, compressor resistance to spin has also dropped due to housing no longer being as pressurised and as a result, the torque required to spin it has dropped massively..
Boom.. Suddenly the Turbine wheels torque massively exceeds the compressors resistance and the turbo spins to speed in an instant!! Sounds great, rapid boost climb!! The compressors acceerating at over 2G 
BUT:
We just hit the same problem again, our huge compressor has made so much boost, so fast, and is trying so hard to push the massive volume or air, that our YB cant use it.... so we start to slow again........
So we went: Fast, slow, fast, slow, or in other words: The turbo is Surging.
As you can imagine, it continues this cycle until it hits the revs your engine consumes all the air.. then your away!!
Downsides to this surge are pretty obvious:
We can have serious bearing wear, due to the excessive loads imparted on the shaft supports.
Compressors have been known to simply explode!!
Worst case scenario, the compressor being slowed rapidly with a turbine still trying to accelerate it can simply do as expected, part company.
Hope this helps to explain in as simple terms as i can put it, the phenomena known as "Turbo Surge."
More info and a big argument, here:
https://passionford.com/forum/viewtopic.php?t=34511
After around 440bhp a T4 is a restrictor. We can push the air harder and harder and make more power, whilst generating more heat, but we are fighting the turbo itself and would be better fitting a bigger more suited turbo, end of story. Peeps in the Ford scene would do well to remember that having to use 2bar of boost is not actually a good thing
Surge:
Surge is caused by the stall, which is worsened by surge, its a vicious circle...
Imagine the way our turbocharger's compressor is driven, right back to basics: The turbine wheel is spun by exhaust gas, utilising also the energy stored in the exhaust gas as latent heat.
This force on the turbine shaft generates torque at the compressor end as they are physically connected. Remember that part as its the key element, Torque
Ok,
Now lets imagine our turbocharger compressing air, forcing it into the engine, the engine is utilising it.. what happens then?
Ok, The engine expells it, and our turbine housing pressure goes up accordingly, the torque applied at the turbine wheel increases, increasing the spin speed and compressor efficiency at the other end. Great chain of events! End Result? boost is climbing nicely.
Ok,
Now imagine this scenario:
The turbo begins to spin, as above, but the compressor wheel is generating more air than we can move and the torque required to spin that huge compressor is not being met? Remember that unless the air is processed by the engine, and expelled as hot, rapidly moving air into the turbine housing, our turbine shaft torque will not increase to spin the compressor faster, and it may well diminish.. our compressor is slowing, braked massively by the compressed air its trying to overcome and increase.....
Result? Compressor starts to slow a little.. (beginings of a compressor stall)
Ok,
So now what?
The engine is still rotating and consuming air, but the turbo has stopped producing an excess, so our engine has now had chance to consume what excess was available and the inlet pressure is now diminishing, the turbine torque is now increasing again...
VERY IMPORTANT:
Remember also that at same time, compressor resistance to spin has also dropped due to housing no longer being as pressurised and as a result, the torque required to spin it has dropped massively..
Boom..
Suddenly the Turbine wheels torque massively exceeds the compressors resistance and the turbo spins to speed in an instant!! Sounds great, rapid boost climb!! The compressors acceerating at over 2G BUT:
We just hit the same problem again, our huge compressor has made so much boost, so fast, and is trying so hard to push the massive volume or air, that our YB cant use it.... so we start to slow again........
So we went: Fast, slow, fast, slow, or in other words: The turbo is Surging.
As you can imagine, it continues this cycle until it hits the revs your engine consumes all the air.. then your away!!
Downsides to this surge are pretty obvious:
We can have serious bearing wear, due to the excessive loads imparted on the shaft supports.
Compressors have been known to simply explode!!
Worst case scenario, the compressor being slowed rapidly with a turbine still trying to accelerate it can simply do as expected, part company.
Hope this helps to explain in as simple terms as i can put it, the phenomena known as "Turbo Surge."
More info and a big argument, here:
https://passionford.com/forum/viewtopic.php?t=34511
31-10-2005, 05:19 PM
#34
15K+ Super Poster!!
T4 is only a 440bhp turbo - afpmsl....
mine made more power than that with out being remotely close to its limit
mine made more power than that with out being remotely close to its limit
Also to Rick a T4 is a genuine 500bhp turbo..providing you have a good spec engine @ 2bar boost..reliable all day everyday
People have different concepts of reliability, but if i wanted a reliable 500hp engine, i wouldnt use a T4.
31-10-2005, 05:29 PM
#35
PassionFord Post Whore!!
Re: Gt 35/40 turbo ??
Originally Posted by marco polo
Hi Peeps
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
The GT30/40 or 35R is a 600hp+ tubo,
The GT30R is good for around 530hp,
Mark
31-10-2005, 06:38 PM
#38
15K+ Super Poster!!
Phil - max boost is difficult to define - max for what exactly? The way you SHOULD define the capabilities of a turbo is by looking at it's compressor map. I don't have a T4 one to hand. The example of the GT3072R i gave above is a turbo designed for 500hp. Im pretty sure u could push it harder for more power, just as you can push a T4 to over 500hp.
My point is that if you are speccing an engine, and want 500hp, it makes no mechanical sense to fit a T4.
My point is that if you are speccing an engine, and want 500hp, it makes no mechanical sense to fit a T4.
31-10-2005, 06:48 PM
#40
Originally Posted by abdr500
how cheap are we talking
Originally Posted by RichardPON
Don't know Marco, but it'd make more than 350bhp with that turbo
You really need more power?
You really need more power?
not really no!!. in all honesty i don't think i ever had a 400+bhp engine allthough did have a graph to prove it to say it was ... it went ok on track but was never 400+bhp or anywhere near that ....
it would be good to have the extra power on tap if you know what i mean
not knocking anyone on here but 500/600+bhp on track theres no way that i could use all of that bhp on track with out lowering the boost some what i would find it totaly hard to drive flat out being honest
Originally Posted by dingy
Marco - personally i would go with a decent t4 - rev limit to 7800/8000 and a pair of karl's cams, a new inlet - either an nms item or the swedish one. And some 1000cc injectors
MUCH less hassle and all you need is a turbo/cams/inlet/injectors and a remap...
Your noise will not be as much of an issue and you don't have to have all the noise of a screamer.
MUCH less hassle and all you need is a turbo/cams/inlet/injectors and a remap...
Your noise will not be as much of an issue and you don't have to have all the noise of a screamer.
Steve
I understand what your saying and that is a good set up see what i don't like about the T4 it's laggy in Sierra .. ok in your car it isn't.. but your only pulling 1000 kg so it does help
I know you can bring a t4 in earlyer say at 3.5k thats all well and good but then i'll lose out the 500 rpm at the top end .. so it's a catch 22
Originally Posted by madevelopments
Originally Posted by marco polo
Hi Peeps
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
I have been offered a GT35/40 (roller bearing) Turbo for very little money brand new and never used (external waste gate type)
right here goes I know that the Gt35 isn't any good a for a 2.0 litre bottom end because they do surge and has been proven that they do on a 2.0 !! and to make them work properly you have to have more cc's to stop the surge !!
do i buy it and do a straight swap with a GT30 what do you recon ??
I'm going to go more power anyway late next yr (if everything goes well) but i want to buy all the bits first so i am undiced to buy this turbo or not
Marco
The GT30/40 or 35R is a 600hp+ tubo,
The GT30R is good for around 530hp,
Mark
I want to run about a gen 530/550 bhp but i want to the turbo to start making boost at the same as my T34.63 does now
so basically same type of boost just with more power so i can use it when needed
I'm happy with my 350bhp because the rest of the car is sorted and thats why it might seem good for 350 bhp it's just that i want more power on tap for next yr
Marco