Turning up the Boost

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Pete Watson

New Member
What are the restricting factors in turning up the Boost?

I am running with a 3071 '.86 & 4"inlet', Power FC, 700inj's, Z32, Tubular Mani, Stainless Elbow & full 3" exh etc etc. I would think that it must have a pretty good flow rate.

I have been told that the maximum boost i can run is 1.6bar, is this correct, i have been told there isn't enough ignition timing to run higher boost, does this make sence? If this is true how can it be overcome, i read about other GTiR owners running 1.7, 1.8bar with the 3071 and maybe more, what am i missing?

Rgs Pete
 
O

oap-r

I love Rob xxx
Pete Watson said:
What are the restricting factors in turning up the Boost?

I am running with a 3071 '.86 & 4"inlet', Power FC, 700inj's, Z32, Tubular Mani, Stainless Elbow & full 3" exh etc etc. I would think that it must have a pretty good flow rate.

I have been told that the maximum boost i can run is 1.6bar, is this correct, i have been told there isn't enough ignition timing to run higher boost, does this make sence? If this is true how can it be overcome, i read about other GTiR owners running 1.7, 1.8bar with the 3071 and maybe more, what am i missing?

Rgs Pete
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What a load o pish :der:

Don't go anywhere near the muppet that told you that :evil:

I think that Rishi has said previously that optimum boost for that turbo was about 2.3 bar :thumbsup:

There is nothing in the spec above that will stop you getting the 450bhp that the turbo is capable of producing unless you still have a std fuel pump :lol: Even the injectors will be good for more than 450 bhp :thumbsup:
 
rossdj1983

rossdj1983

New Member
ive got basically the same set up as you mate, im keeping mine on 1.4 bar. this topic has been covered before if you want to get above the 1.6 barrier you got to start thinking about uprating the ignition system

oap- think your being a little optimistic saying 2.3 bar on a 3071 is its optimum, more like flat out maximum. if your gonna boost that high just get a bigger turbo
 
O

oap-r

I love Rob xxx
rossdj1983 said:
ive got basically the same set up as you mate, im keeping mine on 1.4 bar. this topic has been covered before if you want to get above the 1.6 barrier you got to start thinking about uprating the ignition system

oap- think your being a little optimistic saying 2.3 bar on a 3071 is its optimum, more like flat out maximum. if your gonna boost that high just get a bigger turbo
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You don't always have to upgrade the ignition system just to go above 1.6 bar.It all depends what state your ign system is in,as i've run with 2 bar on the std system and i'm not the only one ;-)

If i ever get mine running right :doh: i won't be upgrading the ign system until i've done another couple of more important things ;-)

iirc,Rishi said max power was produced at 1.8 bar and max torque was produced at 2.3 bar after he looked at the compressor maps.I'm pretty sure that those are the figures that he quoted.
 
C

Crazy

Guest
I want to turn my boost upto 1.8bar too as I have exactley the same setup as you but I was told:

To honest though I don’t really think you are going to gain much by increasing the boost as you are going to create excessive back pressure in the turbine housing , this will cause detonation ,and lower the VE , so we will need to retard the ignition to stop it , this will then lose you the power you have just gained by upping the boost ! !

In most cases once you get to the back pressure level of the turbine ( with integral wastegate turbos ), you are better of keeping more ignition advance , rather than increasing the boost pressure .

You have to take into account the whole package not just what the turbo can do, the turbo compressor can flow x amount of air, but can the cylinder head? Also if the turbo creates excessive back pressure the heat will back up into the cylinder which will give a lower VE, as the engine cannot pass the air through it, this will not show very well on an EGT guage as all the heat is inside the cylinder, not in the exhaust where you are measuring, so you could have low EGT, but still det a piston.

Please, don't think I am being negative, at the end of the day, its your car and I will do anything you want us to do, but I am just trying to make the point that more boost doesn't always mean more power, and you may fit larger injectors, run more boost, but don't get the results you are expecting. I wouldn't be doing my job, if I didn,t try to explain that first !

That is from a well respected engine builder/tuner....................
 
O

oap-r

I love Rob xxx
Crazy said:
I want to turn my boost upto 1.8bar too as I have exactley the same setup as you but I was told:

To honest though I don’t really think you are going to gain much by increasing the boost as you are going to create excessive back pressure in the turbine housing , this will cause detonation ,and lower the VE , so we will need to retard the ignition to stop it , this will then lose you the power you have just gained by upping the boost ! !

In most cases once you get to the back pressure level of the turbine ( with integral wastegate turbos ), you are better of keeping more ignition advance , rather than increasing the boost pressure .

You have to take into account the whole package not just what the turbo can do, the turbo compressor can flow x amount of air, but can the cylinder head? Also if the turbo creates excessive back pressure the heat will back up into the cylinder which will give a lower VE, as the engine cannot pass the air through it, this will not show very well on an EGT guage as all the heat is inside the cylinder, not in the exhaust where you are measuring, so you could have low EGT, but still det a piston.

Please, don't think I am being negative, at the end of the day, its your car and I will do anything you want us to do, but I am just trying to make the point that more boost doesn't always mean more power, and you may fit larger injectors, run more boost, but don't get the results you are expecting. I wouldn't be doing my job, if I didn,t try to explain that first !

That is from a well respected engine builder/tuner....................
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Well we wouldn't want to go any further than what the well respected rip off merchant,sorry tuner :oops: has recommended would we :lol:

Once you get to the point of optimum power,1.8 bar,you won't get any more even if you do up the boost but,you will continue to generate more torque :thumbsup:

Wish i could be bothered to search for that 3071 thread that Rishi replied to :lol:
 
Fusion Ed

Fusion Ed

Active Member
What the ignition can handle is not directly related to what boost you run. More efficient turbo/intercooler set-ups will mean the ignition fails sooner. Less efficient systems or turbos running out side of their efficiency range will be able to run more boost as the charge is less dense, also in summer or higher altitudes with lower air pressure will be able to run more boost on a standard ignition as well.

Its sensible however to pick the worse case scenario of where the ignition system has been seen to fail and assume that above this if yours is ok your lucky but its not guaranteed. You don't really want to get into a situation where by you have to clean the ignition components on a weekly basis just to make sure that it doesn't start to misfire.
 
campbellju

campbellju

Moderators
Staff member
Couple of thoughts:

Firstly, what oap-r, says "load o pish" :lol: :lol:

But.... are we talking about 1.8Bar at the plenum, I'm talking about 1.8Bar at the compressor. My intercooler and pipe work drops just less than 0.1 Bar. Yours might have leaks or an overlarge intercooler meaning its 0.2 or more Bar is dropped. The only norm is the compressor map.

Based on a 3071 and the standard ignition system, I did a lot of research as it was becoming the limiting factor above 1.7Bar at the compressor. It would run 1.7Bar fine with a 0.5mm plug gap. This was the equivalent of 1.6Bar at the plenum and the same as Steve P when he had problems. The boost has only a small amount to do with it, its more the total volume of air and petrol in the mixture that the spark has to jump across the plug gap. I posted up a while ago about an NGK site that with a few graphs showed the relative effects of boost, temperature, compression, coil, rpm on plag gap voltage requirements. When we say 1.7 bar (me included :oops: :oops: :oops: ) its too abstarct to compare. from my own research, IMO, at >400hp, you will need a bigger amplifier on the standard system. at >500 maybe a coil. >600 no idea but I bet the standard leads would still be fine :lol: :thumbsup:


On the 2.3Bar out of a 3071, I'm a pessimist on this at the moment. At 2.3bar ,on the one side of the map you're looking at surge, on the other side you're looking at rapidly reducing efficiency. Once I've sorted my map out properly, I might have a go but I'm already thinking about dropping to 1.4-1.6Bar on a track to control CHT (Cylinder Head Temperature.) I'll leave it to the drag boys.... or is that boys in drag... sorry, one of those days :roll: ;-)

Slightly off topic, Does anyone actually "tune" using an EGT. Tuners don't, otherwise everyone with a tuned car would have a bung in their manifold. I'm not intending to..... det det bang..... oh look, 50deg drop on EGT :doh: :lol: . I was looking at CHT sensors the other day. Far simpler to fit and probably cheaper if I could find a source. Still slow response but more relevant data. Anyone any experience?
 
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Fusion Ed

Fusion Ed

Active Member
CHT sensors are a good idea. They are not as easy to get hold of but are very common in light aircraft data loggers, as you said not good for instantaneous readings, but work well to accompany other sensors. I was reviewing some logs from an on board logger on a Cessna 182 recently. That also had EGT sensors on each cylinder. Trouble is with EGT is its greatly affected by ignition timing, means if you have to pull back ignition the EGT can rise but the cylinder temps not so. (It would show however that your ex valves and turbo could be at risk of running to hot). You can tune to EGT, you just have to know how to read them. This was much more common before Wideband sensors were about as there was not any other readily available (cheap) method to do so. I still know of people who trust EGT more than wideband sensors, as they feel there can be a variance between wideband sensors that you don't get with egt.
 
Fusion Ed

Fusion Ed

Active Member
lol :) I suppose the best way to data log would be a CHT,EGT,Ion,and lambda sensor on each cylinder. Now to find a decent affordable 16 channel data logger..
 
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