Single throttlebody vs multi / stock? - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Asim R32GTR · 26th July 2008, 01:49 PM

Hi

I did a search, but could not find a good answer for this.

I have a R32GTR, it is still running stock multi throttlebody`s.

Has anyone got first hand experience with conversion to single throttlebody?
Did it make much difference?
Are the stock ones restrictive?
etc..

My car is going on the dyno on Wednesday, i need to decide which plenum to use, since i have both available.

Thanks
Asim

palmer77 · 26th July 2008, 06:00 PM

i believe the multi ones give better response......

Madden · 26th July 2008, 06:38 PM

Rk tuning runs standard throttle bodies on his cars. They must be good.

andreasgtr · 26th July 2008, 07:43 PM

Rain runs a single one on his R32. I think it is because you can't get bigger diameter intake plenums with stock throttles. So bigger plenums with higher flow capacity have a single throttle body.
But that's just my try to explain it.

Stachi · 26th July 2008, 07:47 PM

I'm with you on this Andreas.. Would be way to much work to make bigger single throttles and imo wouldn't make that much difference on big power applications.

BTW, have you gone for NOS yet, as advertised on the other forum? :P

Marc

lightspeed · 26th July 2008, 10:11 PM

You can bore out the stock 45mm throttles for either 48 or 50mm throttles.

You can also machine the spindle to have flat sides.

The other mod is PTFE washers to stop the shaft seals blowing out with high boost. Reinik make these.

Madden · 26th July 2008, 10:23 PM

When should you upgrade to ported or big single throttle bodies?

GT-R Glenn · 26th July 2008, 10:47 PM

Standard ones are a serious piece of work do not underestimate hpw good rb26 parts are.
Except the oil pump drive....

Quote:

When should you upgrade to ported or big single throttle bodies?

When you make over 1000 hp

paul cawson · 26th July 2008, 10:58 PM

Quote:

Originally Posted by Madden

When should you upgrade to ported or big single throttle bodies?

RK never changed his plenum even when he ran 9s, but the throttles were over sized.

Madden · 26th July 2008, 11:05 PM

Sounds good to me

Warpspeed · 29th July 2008, 09:35 AM

Advantage of single throttle body is that you can ditch the standard airflow meters and run an aftermarket ECU with a MAP sensor. A single throttle can be made absolutely huge, so any real or imagined flow restriction of the multi throttles will be eliminated. The big plenum volume behind the single throttle damps out the worst of the pressure pulsing, so a MAP sensor at least has a fighting chance of indicating engine load.

There is another aspect to all this as well. Multi throttles are much more cam friendly. If you are running extreme cams, multi throttles will idle smoother and run cleaner and be less lumpy at part throttle lowish rpm.

Multi throttles can cause diabolical problems tuning a MAP based system at small throttle openings, if you are going aftermarket ECU, that uses a MAP sensor, a single throttle will give much better and more stable part throttle mixtures, and as a result, quite likely the potential for much better part throttle fuel economy in a road car.

A single throttle is very popular among the drag racing crowd, but the big disadvantage is throttle response. If you are a drag racer the throttle has only two positions anyway, so who cares about throttle response?

The circuit racers sure do !!!

Try nursing a GTR around a wet race track at full racing speed right on the limit of adhesion. You are driving on the throttle, and you want crisp instant part throttle response, or you are going to go off the track, or be the last car in the pack.

The serious circuit race cars NEVER fit single throttles. The drag racers mostly do. What are you going to use YOUR car for ?

So basically there are several quite different things to think about, mostly depending on how you plan to use your car.

Top end airflow
Throttle response and drivability
Idle quality and lumpiness with big cams.
Compatibility with the ECU, (flow meters or MAP sensor)
Part throttle mixture control and part throttle fuel economy.

Decide what is most important to you and modify accordingly.

Warpspeed · 29th July 2008, 09:58 AM

One last thought on all this.

The cam friendly part of having multi throttles is why a GTR engine can pass strict emissions testing without using variable inlet cam timing. The single throttle RB25DE(T) cannot get away with it. Variable inlet timing is there for passing emissions, and no other reason. It is certainly not a power enhancer.

Variable valve timing does nothing for power, which is why the GTR never had it.

So before you bin the multi throttles, realize that if you plan to run big cams the engine is going to be rougher and lumpier and be a lot more unhappy at idle because of increased exhaust reversion.

tarmac terror · 29th July 2008, 12:48 PM

AT LAST!! some decent info...

Nice one mate.

TT

SamuraiSam · 29th July 2008, 10:27 PM

The stock ITBs give far better throttle response than a single throttle. Just go to google and type in ITB to read about the advantages.

Asim R32GTR · 29th July 2008, 10:57 PM

Warpspeed:

Thanks for the info mate, exactly what i was looking for

Decided to keep stock throttle bodys!

Asim

26th July 2008, 01:49 PM	#1 (permalink)
Asim R32GTR GTR Register Member Join Date: Sep 2003 Location: Norway / Oslo Posts: 928	Single throttlebody vs multi / stock? Hi I did a search, but could not find a good answer for this. I have a R32GTR, it is still running stock multi throttlebody`s. Has anyone got first hand experience with conversion to single throttlebody? Did it make much difference? Are the stock ones restrictive? etc.. My car is going on the dyno on Wednesday, i need to decide which plenum to use, since i have both available. Thanks Asim

29th July 2008, 09:35 AM	#11 (permalink)
Warpspeed GTR Register Member Join Date: Apr 2003 Location: Melbourne Australia Posts: 169	Advantage of single throttle body is that you can ditch the standard airflow meters and run an aftermarket ECU with a MAP sensor. A single throttle can be made absolutely huge, so any real or imagined flow restriction of the multi throttles will be eliminated. The big plenum volume behind the single throttle damps out the worst of the pressure pulsing, so a MAP sensor at least has a fighting chance of indicating engine load. There is another aspect to all this as well. Multi throttles are much more cam friendly. If you are running extreme cams, multi throttles will idle smoother and run cleaner and be less lumpy at part throttle lowish rpm. Multi throttles can cause diabolical problems tuning a MAP based system at small throttle openings, if you are going aftermarket ECU, that uses a MAP sensor, a single throttle will give much better and more stable part throttle mixtures, and as a result, quite likely the potential for much better part throttle fuel economy in a road car. A single throttle is very popular among the drag racing crowd, but the big disadvantage is throttle response. If you are a drag racer the throttle has only two positions anyway, so who cares about throttle response? The circuit racers sure do !!! Try nursing a GTR around a wet race track at full racing speed right on the limit of adhesion. You are driving on the throttle, and you want crisp instant part throttle response, or you are going to go off the track, or be the last car in the pack. The serious circuit race cars NEVER fit single throttles. The drag racers mostly do. What are you going to use YOUR car for ? So basically there are several quite different things to think about, mostly depending on how you plan to use your car. Top end airflow Throttle response and drivability Idle quality and lumpiness with big cams. Compatibility with the ECU, (flow meters or MAP sensor) Part throttle mixture control and part throttle fuel economy. Decide what is most important to you and modify accordingly. Last edited by Warpspeed; 29th July 2008 at 09:47 AM.

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26th July 2008, 06:00 PM	#2 (permalink)
palmer77 GTR Register Member Join Date: Jul 2004 Location: Burton on Trent Posts: 220	i believe the multi ones give better response......

26th July 2008, 06:38 PM	#3 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	Rk tuning runs standard throttle bodies on his cars. They must be good.

26th July 2008, 07:43 PM	#4 (permalink)
andreasgtr Noob Join Date: Jul 2003 Location: Germany Posts: 2,147	Rain runs a single one on his R32. I think it is because you can't get bigger diameter intake plenums with stock throttles. So bigger plenums with higher flow capacity have a single throttle body. But that's just my try to explain it.

26th July 2008, 07:47 PM	#5 (permalink)
Stachi GTROC Member Join Date: Jan 2008 Location: Near Stuttgart, Germany Posts: 834	I'm with you on this Andreas.. Would be way to much work to make bigger single throttles and imo wouldn't make that much difference on big power applications. BTW, have you gone for NOS yet, as advertised on the other forum? :P Marc

26th July 2008, 10:11 PM	#6 (permalink)
lightspeed GTROC Member Join Date: Jul 2002 Location: South-west Posts: 1,803	You can bore out the stock 45mm throttles for either 48 or 50mm throttles. You can also machine the spindle to have flat sides. The other mod is PTFE washers to stop the shaft seals blowing out with high boost. Reinik make these.

26th July 2008, 10:23 PM	#7 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	When should you upgrade to ported or big single throttle bodies?

26th July 2008, 11:05 PM	#10 (permalink)
Madden New Users Join Date: Nov 2004 Location: Berkshire Posts: 2,078	Sounds good to me

29th July 2008, 09:58 AM	#12 (permalink)
Warpspeed GTR Register Member Join Date: Apr 2003 Location: Melbourne Australia Posts: 169	One last thought on all this. The cam friendly part of having multi throttles is why a GTR engine can pass strict emissions testing without using variable inlet cam timing. The single throttle RB25DE(T) cannot get away with it. Variable inlet timing is there for passing emissions, and no other reason. It is certainly not a power enhancer. Variable valve timing does nothing for power, which is why the GTR never had it. So before you bin the multi throttles, realize that if you plan to run big cams the engine is going to be rougher and lumpier and be a lot more unhappy at idle because of increased exhaust reversion.

29th July 2008, 12:48 PM	#13 (permalink)
tarmac terror New Users Join Date: Jul 2003 Location: Hampshire, but Scottish through and through! Posts: 2,622	AT LAST!! some decent info... Nice one mate. TT

29th July 2008, 10:27 PM	#14 (permalink)
SamuraiSam GTR Register Member Join Date: Oct 2007 Posts: 390	The stock ITBs give far better throttle response than a single throttle. Just go to google and type in ITB to read about the advantages.

29th July 2008, 10:57 PM	#15 (permalink)
Asim R32GTR GTR Register Member Join Date: Sep 2003 Location: Norway / Oslo Posts: 928	Warpspeed: Thanks for the info mate, exactly what i was looking for Decided to keep stock throttle bodys! Asim