Size of stock twins vs a single turbo.

[Scott]

Yeah it dumps when you are still in the closed loop sub 0.6 as it hits 4000 rpm it just opens up the flood gates, I could simply prove this by doing a video of my afr and boost controler.

It may even do it at wot open loop from the stand still but you just go through the 4000 rpm point to quickly, it only does it 4000-4300 tops

 

But obviously with the correct sized turbo, its exactly the same a TTC and lots of people run this way with no additional mapping but I would still wantva piggy at least with a afr gauge

 

Need to get a video of the AFR for me. My car definitely doesn't do this

 

Rev the car in neutral and hold around 5k for a few seconds. See what your AFR is.It would be ridiculously rich with no boost. To the point you would get hydrolock IMO.

[Scott]

Obviously it doesn't just always dump fuel in at 4000 rpm for no reason. My comments were for when the #2 turbo is coming online, which only happens if you are already at significant boost with the #1 turbo.

 

I still believe it's pressure related and not rev related. It's just coincidence that the pressure is at it's peak at 4krpm hence why people think it's that rev speed that it happens at.

[mellonman]

Need to get a video of the AFR for me. My car definitely doesn't do this

 

Rev the car in neutral and hold around 5k for a few seconds. See what your AFR is.It would be ridiculously rich with no boost. To the point you would get hydrolock IMO.

 

It dont do it from just reving it , you have to be in some sort of boost but at what boost point im unsure upto 0.6 , I dont know how low it goes , its boost and rev and throttle position and speed of throttle postion related, I did say earlier.

For you sweet heart I will get a video done just to prove to you how a stock ecu works though x

Please be patient with me I have just replaced my manifold and awaiting a oil return fitting to arrive and a time to fit it

Edited April 12, 2015 by mellonman (see edit history)

[V8KILR]

I still believe it's pressure related and not rev related. It's just coincidence that the pressure is at it's peak at 4krpm hence why people think it's that rev speed that it happens at.

 

Yes, of course it can happen at higher rpm as well, as it is the extra fuel for when the #2 turbo comes online. E.g. If cruising at 5000 rpm and then flooring the accelerator, the #2 turbo comes online at say 5500-6000rpm. Around 4000rpm is where it occurs from a low rpm run.

[Scott]

It can happen at lower RPM as well, it's just that the twin tubbies only come on song properly at 4krpm..... hence my point about a more efficient turbo requiring the hit lower down and more fuel at the same boost level.

 

The discussion is going along the lines of the "how many days in a week" thread from the bodybuilding forum now though, so I'm not going to post any more on it. I will only say that boost pressure is not created equal and that 0.5bar from a CT12B and 0.5bar from a GTX30r are 2 completely different things with regards to O2 content and fuel mix required.

 

Best of luck to anyone who blindly follows this train of thought.

[mellonman]

It can happen at lower RPM as well, it's just that the twin tubbies only come on song properly at 4krpm..... hence my point about a more efficient turbo requiring the hit lower down and more fuel at the same boost level.

 

The discussion is going along the lines of the "how many days in a week" thread from the bodybuilding forum now though, so I'm not going to post any more on it. I will only say that boost pressure is not created equal and that 0.5bar from a CT12B and 0.5bar from a GTX30r are 2 completely different things with regards to O2 content and fuel mix required.

 

Best of luck to anyone who blindly follows this train of thought.

 

Exactly this , but its at 4000 injectors go full open from what I can tell from my mapping of closed loop happening , seems lkke you cant even fundge the map sensor to trick the ecu into thinking its got most boost to force it into open loop early ,

I have done a few threads with no conclusive information coming back from it , even with very reterable members posting the same , I will look later tomorrow and link them , therecwas a hole thread with myself and tricky ricky and ian tryinb to find out what exactly caused open loop

Edited April 12, 2015 by mellonman (see edit history)

[Big Supes]

Interesting read going through the posts on this thread. I've never heard of "fuel dump" before in regards to engine management. It sounds incredibly crude.

 

 

I would have thought the ECU merely acts the same way it does throughout the entire driving process; reading signals from its sensors and adjusting timing/fueling as necessary. For example, when it comes on boost, TPS, MAP sensor and airflow meter (in UK/US Spec's case) will tell the ECU to increase fuelling.

Edited April 12, 2015 by Big Supes (see edit history)

[mellonman]

Anyone how has a afr gauge fitted will notice what the stock ecu does regards to the stock sequential map, im suprised this thread has even got this far

Being I have a piggy back ecu and a single turbo I know more them most how it acts and how to over come it

[V8KILR]

Anyone how has a afr gauge fitted will notice what the stock ecu does regards to the stock sequential map, im suprised this thread has even got this far

Being I have a piggy back ecu and a single turbo I know more them most how it acts and how to over come it

 

Ditto. I drove my car for a few years with that same type of setup.

[Big Supes]

My afr gauge will be going in once I go single... Which could be sooner than I had planned as I'm starting to see a little bit of blue smoke. There's no way those horrible twins will be coming off and another set going back on.

[mellonman]

Just to clear this up a little the 4000 rpm dump is maybe not a full 100% injector duty dump , but the 4000 rpm dump is the point that you are still in closed loop ( so have to be at a lower boost then 0.6) as you hit 4000 rpm at this point the stock ecu goes into open loop which no longer uses o2 feed back to try and stay at 14.7 afr

at this point in the stock map its mega rich awaiting the second turbo , ( this could also be for soft gear change for the auto box ). I HAVE AN AUTO SO THIS MIGHT BE WHY I SEE IT AND SCOTT DOES NOT ?

 

closed loop = sub 0.6 bar , 4000 rpm

open loop = anything over 0.6 bar , 4000 rpm .

( this is the part / light throttle )

anything with a fast / hard throttle would go straight into open loop even still as you pass the 4000 rpm you still go mega rich for a split second .

 

if i find time i will do a stock map log and see what the injectors are told to do at that point to see if its 100% duty or not

[CanisLupus]

Boost Cut occurs at 1bar. Slightly under 1bar the Stock ECU does kind of a protection mode with the Injectors opening at 100%(or at least close to 100%).

 

As the Supra has a narrowband Lambda closed Loop only is active when you see around 14,7-15AFR any other AFR Values are not closed loop. There also is NO Learning Procedure from the closed loop mode when entering open loop(confirmed that running E85 for testing purposes when i had an emanage ultimate years ago. Closed loop ran fine after a minute while open loop went crazy lean).

 

First Turbo runs at leaner AFRs with approximately 12-12.5AFR, when second turbo comes online and the fuel system is working correct it drops to low 11s.

 

Everything tried, tested and logged many times

 

Personally i would not recommend running anything other than stock Turbos(EU or JSPEC would not matter that much) on the Stock ECU... apart from the Fuelling the Ignition Timing will not be correct too.

[V8KILR]

Many people use a BCC or FCD and run up to 18 psi on the factory turbos with factory fueling and factory ignition timing without any issues. This works because the factory ECU provided lots more fuel then is needed at 14 psi, allowing a safe A/F ratio even at 18 psi boost. Obviously you must run a high pump octane fuel to do this.

 

So would this be any worse then running a small single (52-55mm) at 14 psi, just under boost cut? I'm pretty sure it wouldn't be any worse and it may actually be easier on the engine as the air from the single turbo at 14 psi would be way cooler then the factory twins would pump out at 18 psi. The only way to know for sure would be to check the A/F and knock sensor readings for both setups on a dyno (at all boost levels) and see who is correct.

 

If the wife's TT Auto Supra turbos crap out, that's what I will be doing. A MasterPower MP-R544 or MP-R545 is what I would use with my spare Threadstone (aka Turbonetics) cast manifold. MP turbo options are:

 

MP-R544 54/77mm compressor, 49/61mm turbine, T3 48, .63, .70, .94

MP-R545 54/77mm compressor, 59/70mm turbine, T3 48, .63, .70, .94, T4 .68, .81, .96, 1.00

Edited April 15, 2015 by V8KILR
Added turbo specs (see edit history)

[Shane]

So, bit of a thread resurrection. I have always fancied doing something along these lines and have come back to this thread often. My turbos are really showing signs of failure which I feel is imminent and have been chatting to James (turtleshead) about this on and off now for a while. He is really keen on the idea of the 6262 for my set up which ultimately together with larger injectors I will probably do.

 

But in the mean time I have a T4 cast manifold on its way and already have a piggyback installed so am thinking of using the manifold together with this http://www.ebay.co.uk/itm/151204601347 with the 440 injectors. Will have to blank off the wastegate port on the manifold and probably do a bit of fabrication to the flange or use an adaptor. What sort of a response do you think this size turbo is going to give with the .63 and .70 and have I overlooked something that will stop this from working?

[Scott]

Don't skimp on the turbo mate. Get a T4 with a proper wastegate and do it right. Go for something similar to the GTX30r (or even that as it's perfect). That along with a cast manifold will be absolutely brutal. You want reliability when the car is done so spend a little more just now and have peace of mind later.

[Scott]

Also, regarding the 4krpm debate.....

 

My car would hit 1.2bar on the 1st turbo and the AFRs would be in the 11's around 3krpm

[Shane]

Don't skimp on the turbo mate. Get a T4 with a proper wastegate and do it right. Go for something similar to the GTX30r (or even that as it's perfect). That along with a cast manifold will be absolutely brutal. You want reliability when the car is done so spend a little more just now and have peace of mind later.

 

Thanks Scott,

 

I will most likely end up with a precision turbo and nice wastegate but am thinking of doing this as an interim thing and a bit of fun/learning really.

 

When you say "(or even that as it's perfect)" are you meaning the one in the link? I quite like the idea of this as its got the internal wastegate and to be honest even if I get charged import duty and vat its still not a lot of cash to see how it works and keeps me going until I really decide what path to go down. I have noticed that most of the cheap smaller turbos available just now seem to be T3 but don't envisage too much of an issue here so long as James suggests it doesn't push the turbo out that bit too much so it fouls the strut tower

[Scott]

Thanks Scott,

 

I will most likely end up with a precision turbo and nice wastegate but am thinking of doing this as an interim thing and a bit of fun/learning really.

 

When you say "(or even that as it's perfect)" are you meaning the one in the link? I quite like the idea of this as its got the internal wastegate and to be honest even if I get charged import duty and vat its still not a lot of cash to see how it works and keeps me going until I really decide what path to go down. I have noticed that most of the cheap smaller turbos available just now seem to be T3 but don't envisage too much of an issue here so long as James suggests it doesn't push the turbo out that bit too much so it fouls the strut tower

 

No I was referring to the GTX30r. It's an amazing turbo for that sort of level of performance (600-ish HP).

 

I genuinely wouldn't touch that turbo with a barge pole. It just screams catastrophic failure to me. If it breaks up internally it could end up in your oil lines or even in your intake. I just wouldn't be taking the chance on such a cheap product.

 

I understand where you are coming from, but for poops and giggles I would buy a known 2nd hand unit on the cheap rather than an unknown new part. Good bearings, impellers, etc are expensive to manufacture precisely with good quality materials. Even a blown second hand turbo that needs a rebuild could be fun taking apart and putting back together.

[Shane]

No I was referring to the GTX30r. It's an amazing turbo for that sort of level of performance (600-ish HP).

 

I genuinely wouldn't touch that turbo with a barge pole. It just screams catastrophic failure to me. If it breaks up internally it could end up in your oil lines or even in your intake. I just wouldn't be taking the chance on such a cheap product.

 

I understand where you are coming from, but for poops and giggles I would buy a known 2nd hand unit on the cheap rather than an unknown new part. Good bearings, impellers, etc are expensive to manufacture precisely with good quality materials. Even a blown second hand turbo that needs a rebuild could be fun taking apart and putting back together.

 

OK, pretty much what James's thinking is too in terms of a decent turbo.

[mellonman]

Also, regarding the 4krpm debate.....

 

My car would hit 1.2bar on the 1st turbo and the AFRs would be in the 11's around 3krpm

 

Of corse its would it would already be in open loop

the 4k debate is in regards to maintaning closed loop building boost IE: part throttle . closed loop afr 14.7 will stay until 4k and at that point it goes off scale rich as it goes into open loop. ( this maybe the open loop map at the lower boost setting im not sure ? or maybe the stock auto gear box protection to drop power at gear change i just dont know.

 

since i have done my manifold and down pipe swap i have more in formation on this now being you can make more then 0.7 bar and still be in closed loop (with slowly building boost up until 4k rpm )

so fudging the map sensor to force open loop so you can map fueling correctly as 0.7 bar on a single turbo is way to much boost even for part throttle can not be done .

you do have to fudge the o2 feed back to get the correct fueling in the lower rpm part throttle stuff.

I hope ive explained it a little better ?

[Scott]

I don't get it at all bud. I'm only going from experience.

 

If my injectors ran full duty at 4krpm the car would run mega rich. It didn't, it ran 11.2-ish, from 3krpm to 8krpm with a lean spot (12-ish) at the 4k transition. If the same amount of fuel was going into the cylinders at 4krpm vs 8krpm then it stands to reason that the bore would be WAY richer at 4krpm than 8krpm.

 

I don't get any of it at all, it just doesn't make any sense to me. To have the same AFR with the same fuel at different RPM just doesn't make any sense to me.

[mellonman]

but to get your afr down to 11 by 3k you would need to have already gone into open loop and would be making more boost then the 0.7-0.8 at 4k

 

I cant tell if they go 100% duty at this transition point ONLY with out logging which I cant be bothered to do as i have different injectors , I think you think im saying that they stay 100% from 4k they dont .

 

All i can say is my car when keeping in closed loop so small throttle input and slowly building boost staying at stoick 14.7 afr at 4k rpm swings from stoick to mega rich way passed 10 afr for maybe 200 rpm.

 

so anyone fitting a single turbo that spools quickly will need some sort of closed loop fueling adjustment

[Scott]

 

so anyone fitting a single turbo that spools quickly will need some sort of closed loop fueling adjustment

 

That's what I've been saying from the beginning that everyone and their granny, including yourself, was arguing against me

[mellonman]

That's what I've been saying from the beginning that everyone and their granny, including yourself, was arguing against me

 

I never argued with you about saying the stock fueling is no good for single turbo ! just about the 4k dump !

 

when your single turbo on a stock ecu with a piggy back you can see it more then you can with stock twins

[Scott]

I never argued with you about saying the stock fueling is no good for single turbo ! just about the 4k dump !

 

when your single turbo on a stock ecu with a piggy back you can see it more then you can with stock twins

 

After 4k I would have thought that the aim of the ECU is an AFR of 11. 440cc injectors at 100% would, in my mind, be way lower. Off load with no boost at 4krpm would see a MUCH lower AFR than 4k rpm on load with 1.0bar of boost. This suggests that there is a control of some sort. I don't know what it is, but anything un-controlled would see much more varying AFRs at the varying situations.

 

There's no way that off load would be the same as on load and there's no way that 4krpm would see the same AFR as 6k+rpm without some sort of control in place.

 

I agree there will be a fuel swing at that point, as that's just the way it was designed, but fuel dump is far too crude a term. I don't know how low AFRs can possibly go but 6 440cc injectors at anywhere near 100% duty would see bore wash in no time when the o2 levels were so low (0 boost).