Porting intake manifold, larger tb vs. itb's

[jibbby]

Well, this is sorta on topic. Probably several here have already seen this photo over on the GT40s website, but just look at the intake ports on this Ferrari 360 Modena 5 valve head. Isn't this some artwork? The owner of the motor says this is straight from Ferrari - no porting done at all:

John, If you ever get the chance to go to Las Vegas, NV. have a look at the Ferrari museum...It has all the Ferrari parts, different designed Ferrari motors, individual hand held parts inspections, etc.. Just a good history breakdown on Ferrari motors in general which you probably already know..I spent hours in that museum in awe... Ferrari really is a step above all other motors in my opinion...

 

[jibbby]

I had a few pics of ITB 1uz.. setups from years past and I will post the pics since it is some what related to this thread... These bad boys do look awesome...

Also, this is a pick of the MAF body that comes stock on the SC400's..As you can see it isn't very wide...So with 8 ITB's all the intake airflow would have to pass thru that.. Just looks like it would almost defeat the whole purpose.......

 

[Jake Breyck]

Also, this is a pick of the MAF body that comes stock on the SC400's..As you can see it isn't very wide...So with 8 ITB's all the intake airflow would have to pass thru that.. Just looks like it would almost defeat the whole purpose.......

rember not all the intake ports are pulling air all of the time if they where all pulling air constantly then you may have a point.

 

[jibbby]

I have a point regardless...

If you were to set up the ITB's with the MAF intact your going to have a big air tight cover where eight throttle bodies are pulling in air thew that small MAF body and the airflow sensor...Now even though the eight pistons are not firing at the same time the intake airflow should be more aggressive I would think... With increased throttle response from the throttle bodies increased and immediate intake air flow must be present...Common logic suggests this?

You can't rattle me anymore Jake so don't even try..Waste of time...

 

[ed_ma61]

increased throttle response from the throttle bodies increased and immediate intake air flow must be present...Common logic suggests this?

?
no it doesnt

throttle response has absolutley zero to to with CFM, only rate of response between throttle and valve

CFM is ony related to absolute power output. ITB's themselves do nothing to peak hp or CFM of an engine. for a given power level/CFM rate if the MAF is not the choke point, it still will not be the choke point for the ITB assembly

 

[andrew k.]

I read all this with great interest. For me I have elected to make my own inlet plenum and intake runners for a twin turbo 1UZ. Relocating a single 83mm Nissan throttle body to the front of the air inlet coming directly from the IC outlet. Low compression pistons and larger injectors was correct for what I wanted. A larger TB works best for me.

 

[cribbj]

Andrew, the possibility of using ITB's for an FI application is going to move this interesting discussion into a yet another area.

For me, the primary technical justification for ITB's is the improved throttle response you can gain with them on an NA motor. Simplistically, giving each hole its own butterfly means that hole isn't competing with the other holes anymore for the same air.

In a turbo application, the response of the engine is probably going to be more affected by the inertia of the turbo upstream. In some conditions, (such as prespool) the turbo is actually going to add a restriction in the intake, so it really wouldn't matter whether the motor is "pulling" from one big butterfly or 8 little ones. When the throttle is banged open, the poor motor is trying to suck air through a "straw" which is the entire intake system, c/o piping, intercooler, more piping, turbo, more piping, MAF and an intake filter. It would be interesting to put a pressure sensor in the intake system and see just how much the air pressure drops in these instances. (This is like trying to suck a thick milkshake through a small straw.)

But then, this situation should change completely once the turbo is on boost (it's now "pushing" more air through the straw than the motor wants) Now, when the ITB's are cracked open a bit more, the response should be "much" faster than having a single TB just upstream of a fairly large plenum, with a pretty big deltaP separating the pressure in that plenum and the pressure upstream of the TB.

To me, this sounds like a great argument for having ITB's in a supercharged application, and having positive pressure available in the system all the time, just in front of the butterflies. It probably wouldn't be practical to try this with a roots or twinscrew sitting on a Richwood manifold due to the lack of space, but it would be waaaaay cool to try with one of the centrifugal SC setups. I don't know if KC is reading this, but he's been fighting the "lag" monster recently, and has been fine tuning his setup to try and reduce the volume of the intake system between the centrifugal SC and the motor. But.....if he had that entire volume pressurised all the time with more air than the motor needs, then by definition, there should be zero lag.

Does this make any sense, or is it time to put the crack pipe down?

 

[SC400TT]

Andrew, the possibility of using ITB's for an FI application is going to move this interesting discussion into a yet another area.

For me, the primary technical justification for ITB's is the improved throttle response you can gain with them on an NA motor. Simplistically, giving each hole its own butterfly means that hole isn't competing with the other holes anymore for the same air.

In a turbo application, the response of the engine is probably going to be more affected by the inertia of the turbo upstream. In some conditions, (such as prespool) the turbo is actually going to add a restriction in the intake, so it really wouldn't matter whether the motor is "pulling" from one big butterfly or 8 little ones. When the throttle is banged open, the poor motor is trying to suck air through a "straw" which is the entire intake system, c/o piping, intercooler, more piping, turbo, more piping, MAF and an intake filter. It would be interesting to put a pressure sensor in the intake system and see just how much the air pressure drops in these instances. (This is like trying to suck a thick milkshake through a small straw.)

But then, this situation should change completely once the turbo is on boost (it's now "pushing" more air through the straw than the motor wants) Now, when the ITB's are cracked open a bit more, the response should be "much" faster than having a single TB just upstream of a fairly large plenum, with a pretty big deltaP separating the pressure in that plenum and the pressure upstream of the TB.

To me, this sounds like a great argument for having ITB's in a supercharged application, and having positive pressure available in the system all the time, just in front of the butterflies. It probably wouldn't be practical to try this with a roots or twinscrew sitting on a Richwood manifold due to the lack of space, but it would be waaaaay cool to try with one of the centrifugal SC setups. I don't know if KC is reading this, but he's been fighting the "lag" monster recently, and has been fine tuning his setup to try and reduce the volume of the intake system between the centrifugal SC and the motor. But.....if he had that entire volume pressurised all the time with more air than the motor needs, then by definition, there should be zero lag.

Does this make any sense, or is it time to put the crack pipe down?

Great explanation John, or should I say tutorial? Your last comment was very funny!!! HA HA HA HA HA....

Ryan

 

[jibbby]

?
no it doesnt

throttle response has absolutley zero to to with CFM, only rate of response between throttle and valve

CFM is ony related to absolute power output. ITB's themselves do nothing to peak hp or CFM of an engine. for a given power level/CFM rate if the MAF is not the choke point, it still will not be the choke point for the ITB assembly

Ok, then I am wrong, I will take your word for it...I would have guessed with more throttle bodies and faster throttle response that would demand a higher CFM as the engine I would have thought turns faster and more aggresive then normal... I stand corrected, and I will take your word for it... Thanks for the correction...

Still there has got to be some restrictions on a stock MAF body...

 

[jibbby]

Cribbj good last post...

It makes sense to go with ITb's if you have a Charger or turbo's strapped onto your exhaust pipes..Like a Centrifugal charger or exhaust turbo's...I am sure you would see the benefits as John suggested in his above post....

Would it even be possible to have ITB's with a root blower? That I would like to see...

 

[JBrady]

The ultimate ITB is variable valve activation.

Using the actual intake valve as the throttle body has so many advantages.

An inventor from Greece has devised an elegantly simple variable valve activation system. Unfortunately it would be very difficult to apply to bucket on cam engines such as the xUZFE but is fairly simple on almost any other design.

Very much worth reading and understanding.

http://www.pattakon.com/vvar/HelpRoll.htm

Here is the system running on a Honda engine

http://www.pattakon.com/vvar/OnBoard/A1.MOV

An image showing just a few of the infinite possible valve lift possibilities.

 

[striker]

BMW has an engine without a throttlebodie(s) at all,

applying throttle is done by setting the valvetrain timing and lift. sort of super Vanos.

Erol can you perhaps awnser a few of the questions I asked, just say so if you'd rather not, no hard feelings offcourse.


Grtz Thomas

 

[JustenGT8]

In a turbo application, the response of the engine is probably going to be more affected by the inertia of the turbo upstream. In some conditions, (such as prespool) the turbo is actually going to add a restriction in the intake, so it really wouldn't matter whether the motor is "pulling" from one big butterfly or 8 little ones. When the throttle is banged open, the poor motor is trying to suck air through a "straw" which is the entire intake system, c/o piping, intercooler, more piping, turbo, more piping, MAF and an intake filter. It would be interesting to put a pressure sensor in the intake system and see just how much the air pressure drops in these instances. (This is like trying to suck a thick milkshake through a small straw.)

But then, this situation should change completely once the turbo is on boost (it's now "pushing" more air through the straw than the motor wants) Now, when the ITB's are cracked open a bit more, the response should be "much" faster than having a single TB just upstream of a fairly large plenum, with a pretty big deltaP separating the pressure in that plenum and the pressure upstream of the TB.

To me, this sounds like a great argument for having ITB's in a supercharged application, and having positive pressure available in the system all the time, just in front of the butterflies. It probably wouldn't be practical to try this with a roots or twinscrew sitting on a Richwood manifold due to the lack of space, but it would be waaaaay cool to try with one of the centrifugal SC setups. I don't know if KC is reading this, but he's been fighting the "lag" monster recently, and has been fine tuning his setup to try and reduce the volume of the intake system between the centrifugal SC and the motor. But.....if he had that entire volume pressurised all the time with more air than the motor needs, then by definition, there should be zero lag.

Does this make any sense, or is it time to put the crack pipe down?

This indeed makes sense Cribby, but a coupla points. As you say in the 2nd para, once you hit positive pressure the turbo/SC is providing more air than the engine actually wants which gives good throttle response.

In reality, at zero boost and even slight vac the turbo if providing more air to the engine that if there was no turbo. This means that in nearly all caes the turbo provide better throttle response than an n/a engine!!

Where people get confused is that the big rush of power can take that extra split second and that's the 'lag' you feel. In reality even though you may feel lag, the car is actually faster and responding better than n/a.
Of course, reducing this lag is still worth the effort but i strongly believe people make to big an issue of it and don't understand what is actually going on.

There are probs with having positive pressure all the time though so it's not as desireable as you might think John. For a postive displacement SC, it places alot of strain on the SC and parastici losses go thru the roof. Fuel economy would go out the window too.

Basically what you need is a system that goes from vac to positive flow quickly. Any well designed SC or turbo setup will do this and that's part of the art i guess

By way of real life confirmation. Line the GT8 up against a n/a version. Now pick any gear, any rpm, any throttle position and the GT8 will beat every time and most often slaughter the n/a version. Turbo FTW

 

[rms]

Erol can you perhaps awnser a few of the questions I asked, just say so if you'd rather not, no hard feelings offcourse.


Grtz Thomas

Happy to answer questions Thomas, last reply was
http://lextreme.com/forums/showpost.php?p=82466&postcount=92

Have I missed something ? :thinkerg:

 

[XR8tt]

Justin.. YES how much lag is there on an n/a engine with 400+ h.p ??
If it did it would be at the higher rpm range...
Turbo's as in N/A you only have to go through this once. At the start.. Unless you have bad ratio's...
I'm making over 600 rwhp with 75mm single throttle body..
With previous tune and std 65mm it was just over 500 rwhp..
BUT other mods were done including twin 3" exhaust, more boost, and better fuel pumps...Itb's are more for n/a and race engines...

 

[JBrady]

BMW has an engine without a throttlebodie(s) at all,

applying throttle is done by setting the valvetrain timing and lift. sort of super Vanos.

Erol can you perhaps awnser a few of the questions I asked, just say so if you'd rather not, no hard feelings offcourse.


Grtz Thomas

YES, that is what I posted in the Patakon post above, NO throttle bodies at all. The intake valves become the throttles like the BMW but the above system is very simple and could be used on most engines.

 

[rms]

With a road or drag car the so called 'turbo lag' is really not an issue.
When the car is for circuit racing however there is an issue with turbo cars and a better definition is 'non linear part-throttle response'.

A major problem with the 'turbo era' Formula 1 cars was mapping the 'fly by wire' throttle linearity with power delivery. It was probably the single most significant factor to getting competitive lap times. Ayrton Senna spent hours with the Honda engineers getting this aspect to his liking.

 

[cribbj]

There are probs with having positive pressure all the time though so it's not as desireable as you might think John. For a postive displacement SC, it places alot of strain on the SC and parastici losses go thru the roof. Fuel economy would go out the window too.

I hear you about the increased parasitic losses, but those could be reduced by judicious use of the unloader (bypass) valve. What I'm proposing is to fine tune the unloader valve to "follow" the manifold pressure a little more closely (of course with ITB's it's going to be a little tougher to GET a manifold pressure, but you use an accumulator with 8 lines, etc.)

Obviously, you don't want a situation where you're trying to maintain an idle with 500 mmhg vacuum on one side of the butterflies, and the supercharger trying to push 10 psi of boost past them.

The advantage I'd see of this, is moving the butterflies further downstream, thereby reducing the volume of air which normally sits between them and the heads which has to be pressurised every time.

Of course this setup isn't going to give you quite a step response to the step input of banging the throttle open, but by reducing the volume that has to be pressurised each time, it should do wonders for lag.

But at the end of the day, this is just keyboard conjecture...... It would be interesting to hear about real world cases where it's been tried.

 

[Jake Breyck]

I wouldnt think it would be too hard to setup a bypass valve that automaticly opens at very low throttle so there is never boost at idle or low engine speeds but once the trottle passes a set point the motor spings to life with instant boost. could be done eletronicly and use tps as input. im also sure many aftermarket ecus could use an aux output to control the valve basied on tps.

this wouldnt have to be an on off thing eather but a gradual closing of the bypass of sorts.

 

[JustenGT8]

Pretty much what i want to try John seeing the SM2 has the smarts. The problem i'm findling is sourcing a solenoid valve to do the job.....bugger all suitable and what is is waaaaayy too large.

next option is to control the vac single to the actuator but what i really want is a valve i can open under boost as well to assist with turbo flow and parasitic drag.