Swapping in a larger Throttle body

[Izza]

Hi folks, 

I own a Vitz 1.0L (1KR-FE) car. I'm looking for options to increase the initial throttle response - and thought whether swapping the throttle body for a larger one, possibly the throttle body from either Vitz 1NR-FE (1.3L) or 1NZ-FE (1.5L) - would make any difference. The stock throttle body inlet diameter is 38 mm as I found. When swapping, I suppose matching the larger throttle body outlet to the intake manifold would need to be sorted, but I guess a matching plate (starting from the new throttle body diameter to gradually reduce to fit to the intake manifold) would do the trick. In addition, will be coupling this with a CAI.

My questions are:

• Anyone who has attempted the same here, who can share their experience?
• Could this give a improvement in the throttle response? Or is it not worth it?

Thank you.

[ajm]

If you just change throttle and not the combustion maps, it will drive the air/fuel management system nuts and worsen performance and emissions on transient operation

Edited March 14, 2022 by ajm

[iRage]

Okay...so what exactly are you looking for ? Are you looking for quicker throttle RESPONSE or are you looking for more power ?

Putting a larger throttle body means sending in more air (and subsequently you will have to make sure proportional fuel feed as well) which means you get an improvemen in power. No..this does not necessarily mean that your throttle RESPONSE will increase that much (if at all).

If what you are looking for is that the response you get from the engine be more quicker than what it is..then in modern cars you are looking (for the most part) a "tune"/"remap"/etc...

Look at getting a compatible throttle response controller. TOM's had a Toyota licensed unit for the VItz (KSP130 inclusive).

Check the link below:

https://www.tomsracing.co.jp/sv/products/car/typedetailseng.php?carID=1106&typeID=2279

Tuners like HKS also has them....or you can just simply go to someone like Sabry or Kelum W (not the Doc) and ask what he/they can do to the tune of the car to make it respond better. 

[Izza]

Thanks @ajmand @iRage.

I actually thought the ECU will compensate with adding more fuel. Isn't that the case ? And yes, can get a ECU tune too.

 

1 hour ago, iRage said:

Okay...so what exactly are you looking for ? Are you looking for quicker throttle RESPONSE or are you looking for more power ?

Putting a larger throttle body means sending in more air (and subsequently you will have to make sure proportional fuel feed as well) which means you get an improvemen in power. No..this does not necessarily mean that your throttle RESPONSE will increase that much (if at all).

 I'm looking for quicker throttle response yeah. wouldn't the ECU add more fuel when it detects the larger amount of air via the MAF sensor? 

 

1 hour ago, iRage said:

If what you are looking for is that the response you get from the engine be more quicker than what it is..then in modern cars you are looking (for the most part) a "tune"/"remap"/etc...

Look at getting a compatible throttle response controller. TOM's had a Toyota licensed unit for the VItz (KSP130 inclusive).

Check the link below:

https://www.tomsracing.co.jp/sv/products/car/typedetailseng.php?carID=1106&typeID=2279

Tuners like HKS also has them....or you can just simply go to someone like Sabry or Kelum W (not the Doc) and ask what he/they can do to the tune of the car to make it respond better. 

Thanks, did not know about throttle response controllers. Will certainly check them out. And I assume I can anyway do a tune after fitting a throttle response controller (If I'm able to get one down amidst this situation)?
 

[iRage]

5 hours ago, Izza said:

I actually thought the ECU will compensate with adding more fuel. Isn't that the case ? And yes, can get a ECU tune too.

 

5 hours ago, Izza said:

I'm looking for quicker throttle response yeah. wouldn't the ECU add more fuel when it detects the larger amount of air via the MAF sensor? 

Yes...but the thing is the base tune of your ECU is programmed to do that only within a small threshold. So putting a larger throttle body for more air does not mean there will be as much fuel as it needs getting pumped in.  The car may send in more fuel to whatever air flow changes to maintain the car's default levels of performance (and depdning on the car's system actually restrict the air being flown in). WIll there be a improvement ? yes...but then the improvement might not justify the investment just to swap a throttle body as it would be minute (like how it feels when you swap in an old air filter for a new one). In which case, you might as well look at improving air flow of the current setup (cold air box, performance air filter, etc..). If the car has a drive by wire system (i.e. electronic "pedal") then that adds another dimension where you might not see that much improvement at all because now the presets are limiting the throttle control to operate within its programmed thresholds (so that the car doesn't act and feel bonkers to unsuspecting users when the car drives through varying environments with differing air pressures and flows).

If you are looking for the whole: not waiting for 30 seconds till the engine acts up after you step on the gas and not actually looking for significant power gainst...then I would first say you will have to take a more complete lok at it. Easiest is to look at the ECU and throttle response controller (this can be expensive through), which will give you some control over fuel and air flow controls.

Also, you mentioned using the throttle body of a 1.5L or a 1.3L variant..are you sure the components are compatible ?

 

Edited March 15, 2022 by iRage

[Izza]

4 hours ago, iRage said:

 

Yes...but the thing is the base tune of your ECU is programmed to do that only within a small threshold. So putting a larger throttle body for more air does not mean there will be as much fuel as it needs getting pumped in.  The car may send in more fuel to whatever air flow changes to maintain the car's default levels of performance (and depdning on the car's system actually restrict the air being flown in). WIll there be a improvement ? yes...but then the improvement might not justify the investment just to swap a throttle body as it would be minute (like how it feels when you swap in an old air filter for a new one). In which case, you might as well look at improving air flow of the current setup (cold air box, performance air filter, etc..). If the car has a drive by wire system (i.e. electronic "pedal") then that adds another dimension where you might not see that much improvement at all because now the presets are limiting the throttle control to operate within its programmed thresholds (so that the car doesn't act and feel bonkers to unsuspecting users when the car drives through varying environments with differing air pressures and flows).

If you are looking for the whole: not waiting for 30 seconds till the engine acts up after you step on the gas and not actually looking for significant power gainst...then I would first say you will have to take a more complete lok at it. Easiest is to look at the ECU and throttle response controller (this can be expensive through), which will give you some control over fuel and air flow controls.

Also, you mentioned using the throttle body of a 1.5L or a 1.3L variant..are you sure the components are compatible ?

 

Thanks. I checked the some of the popular throttle controllers like P***l C*******r, but yeah those are awfully expensive. No idea about the price of the Toms. Guess it should be pretty expensive too.  

There are few people who seem to have done this. Therefore I thought the throttle body swap should be workable.

Edited March 15, 2022 by Izza

[Izza]

So, I actually went ahead and tried this out. Did it out of curiosity mostly, to find out what happens. And yeah it does change the throttle response characteristics, but could not drive around a lot after the mod. Also, I'm still to pair this mod with a better air intake. Will post the results once I do. 

[iRage]

On 5/1/2022 at 1:00 PM, Izza said:

So, I actually went ahead and tried this out. Did it out of curiosity mostly, to find out what happens. And yeah it does change the throttle response characteristics, but could not drive around a lot after the mod. Also, I'm still to pair this mod with a better air intake. Will post the results once I do. 

Nice !

As we discussed, yes the throttle characteristics would change...but yes..upgrading the air intake, fuel feed and subsequently air out-flow will help gain some increases in power and torque. So it might feel like a better feel once those mods are made.

[Izza]

Hi, 

This is a short summary of what I did.

• Got the throttle body from a 1300cc engine (1NR). This has a significant size different compared to the Vitz 1KR original one. However the bolts positions which fixes the TB to the intake manifold are the same.

 

• Swapped out the control boards from the original one to the new one.

 

• The manifold side opening is around 35mm while the new TB opening is about 45 mm. Therefore, made a small adaptor plate from a block of aluminium to have a gradual reduction from 45mm to 35 mm. Thickness of the aluminium block was 3/4 inches. Its similar to a throttle body spacer like below, but not neat as this of course Got some help from a local lathe shop. Also cut out a small gasket from gasket paper to fit between the adaptor plate and new TB.

 

• The installation order from the side of the intake manifold was Manifold with original gasket | throttle body plate | custom gasket | new throttle body
• Afterwards got some help to fabricate a small CAI (pipe diameter: 3") and used an unbranded cone air filter with a dust cover, and was good to go

Improvements that I noted:

• Induction sound change due to the CAI. Had a bit of a growl in it now. For me was not really important tho - I know many of you petrol heads will disagree
• Increased pulling power in the mid to high RPM range. After about 4000 RPM it has a improvement in the pulling power, but not anything ground breaking - can't expect anything of that sort with this 1KR engine.

Downside:

• Decrease in torque/pulling power in the lower RPMs. I think this could be because of the intake air velocity being low due to the wider TB and air intake.

So yeah, this was my experience after doing it. Since this mod kind of reduced my low end torque, I have reverted back to the original setup. However, I now use a drop in K&N air filter with some custom air tubing routed to an opening in the front grill of the car where it can suck in colder air specially when the car is moving. The original air tubing sucks in air just from the left side of the engine, which IMO is not the best place for a cold air feed.

Edited July 17, 2022 by Izza

[mazdaspeed]

ON the same line of thought .....

I was reading up on a Throttle spacer ..... Basically to improve circulation of air inside the throttle itself...

Any one done a similar modification ?

 

[Izza]

On 7/18/2022 at 6:19 AM, mazdaspeed said:

ON the same line of thought .....

I was reading up on a Throttle spacer ..... Basically to improve circulation of air inside the throttle itself...

Any one done a similar modification ?

 

Just putting down what I think.. Spacers would work in engines with carburetors.. it could improve the air fuel mixture uniformity since fuel and air is mixed inside the carb and then you get this swirling/circulating effect right after by this spacer.. but with EFI, even if the air swirls just after the TB, not sure how it can have the same effect.. Again, this is just what I think. 

Edited July 21, 2022 by Izza

[iRage]

Can I ask how much the conversion cost ?

 

[Izza]

2 hours ago, iRage said:

Can I ask how much the conversion cost ?

 

Reconditioned TB = 15k

Aluminum spacer = 2k for material and lathe work

Extra long bolts and nuts = 0.5k

Gasket paper = 0.5k 

Other stuff I already had, including a cone air filter (unbranded), silicone couplers etc. I did not go for a proper CAI, but assembled one from PVC pipes and a few bends. Idea was to test it out first. 

[iRage]

So all in all...(apart from the stuff you already had) you are at 18K...lets just round it up to 20K. For what you could gain, would you say the cost is justifiable ? Would you recommend it to someone else ? 

[Izza]

1 hour ago, iRage said:

So all in all...(apart from the stuff you already had) you are at 18K...lets just round it up to 20K. For what you could gain, would you say the cost is justifiable ? Would you recommend it to someone else ? 

For this specific engine (1KR-FE), I think there weren't a lot of gains. Hence, for this specific case only, I would say its not worth it. But depends on what you expect really. But if it was a larger engine / an engine with forced induction IMO it could have been different.

[mazdaspeed]

On 7/21/2022 at 8:58 AM, Izza said:

Just putting down what I think.. Spacers would work in engines with carburetors.. it could improve the air fuel mixture uniformity since fuel and air is mixed inside the carb and then you get this swirling/circulating effect right after by this spacer.. but with EFI, even if the air swirls just after the TB, not sure how it can have the same effect.. Again, this is just what I think. 

Thanks a good thought as well .... should see if the foreign guys have used this and if they had any improvements