Throttle Body Spacers?

[Tanner]

Are there any benefits, (worth pursuing), with the addition of a throttle body spacer in a 4.0?

[ftpiercecracker1]

I once found a high dollar one in a JY and decided to put it on for the heck of it, zero noticeable improvement. Its 'supposed' to increase intake charge speeds or create some kind of air vortex that causes the fuel/air to mix better, but i dunno the exact science behind it. :dunno:

 

Bottom line:

 

TB spacers = no improvement = waste of money

[Incommando]

Snake oil

[cruiser54]

Junk.

 

Get a 60mm throttle body from www.strokedjeep.com

[Tanner]

Cool thanks for the input guys.

[Keyav8r]

Regardless of whether the spacer increases the intake charge speed and/or creates a vortex it will have no effect on the air/fuel mix as the fuel is injected at the intake valve port. The larger throttle body (60 mm) should have a performance improvement as it will allow more air flow resulting in a more efficient filling of the combustion chamber.

It may be necessary to change to higher flow injectors to get the most benefit from the larger throttle body. Don't know if there is any way to "recalibrate" the ECU to compensate for the higher air flow rate so that it injects the correct amount of fuel to achieve the proper air to fuel ratio.

[cruiser54]

Regardless of whether the spacer increases the intake charge speed and/or creates a vortex it will have no effect on the air/fuel mix as the fuel is injected at the intake valve port. The larger throttle body (60 mm) should have a performance improvement as it will allow more air flow resulting in a more efficient filling of the combustion chamber.

It may be necessary to change to higher flow injectors to get the most benefit from the larger throttle body. Don't know if there is any way to "recalibrate" the ECU to compensate for the higher air flow rate so that it injects the correct amount of fuel to achieve the proper air to fuel ratio.

No need to change the injectors. They're plenty big enough. 

 

Put some 0 280 155 746 injectors in it from a Volvo. 

[Herc]

Thw ECM's have a built in 10% +/- fuel curve if I recall correctly. Factory compensation for dufferent altitudes.

[cruiser54]

Altitude compensation is done by the MAP. 

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested. 

[outlaw star]

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

[Jeep Driver]

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

 

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

[cruiser54]

 

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

 

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

 

Not that simple. The flow rate of the individual injector comes into play. A real big injector will not trim back enough given a certain pulse from the ECU to allow the idle to be lean enough. 

[outlaw star]

 

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

The MPFI 2.5L yes, not the TBI 2.5L. Theyre both EV1 style 19lb hr injectors. The trick in switching injectors is to find one that mists the fuel instead of just spraying it. Think of it like the dual spray pattern on a bottle of Lysol, 409 or whatever kitchen cleaner you use. Now one setting is just a stream, the other is more of a conical spray. Now air and fuel need to mix evenly for a better, more efficient burn. So which pattern do you think would be best if you shot fuel outta that cleaner bottle? The conical pattern because the fuel is a finer mixture than if it just shot out like a stream.

As for the duty cycle of an injector opposed to it's flow rating, take the 19lb number, this is how much fuel the injector will push if the needle is held constantly open. This is where duty cycle is used. Duty cycle is the amount/length of time the needle in the injector is held open by the ECU. The injector, much like the VE of a carb, never sees 100% of it's duty cycle so the 19lb unit operates more like a 15-16lb unit.

By switching to lets say a Cobra 24lb injector, you may gain a little more pressure for that brief cycle but the ECU still operates at it's pre-programmed duty cycle.

 

When you adjust things like MAP, O2, Temperature Sensors, etc, the ECU makes fine adjustments to it's duty cycle to adjust the A/F ratios. This is where the slightly larger flow rate helps out because the larger injector doesn't have to work as hard to flow more fuel.

 

Sorry for the lengthy reply, I'm just trying to awnser/explain your question as simple as I can for you.

[yxmj]

You all changed the answer to injectors.....i am going back to the OP.. :thumbsup: sorry if my spelling is off

 

The idea of space comes from old carbureted motors …..go look at old school v8s with just high rise manifold and single carb effective…yes…..but carbureted……they allowed the fuel an air more time to atomize and mix…..more bang for your buck…(same sales pitch in  their ads but wrong)….this is totally impossible for a tbi or an mpfi motor……the fuel delivery is different…….

[outlaw star]

You all changed the answer to injectors.....i am going back to the OP.. :thumbsup: sorry if my spelling is off

 

The idea of space comes from old carbureted motors …..go look at old school v8s with just high rise manifold and single carb effective…yes…..but carbureted……they allowed the fuel an air more time to atomize and mix…..more bang for your buck…(same sales pitch in their ads but wrong)….this is totally impossible for a tbi or an mpfi motor……the fuel delivery is different…….

Sorry, got sidetracked. Lol. Correct, great for carbs and TBI, crappy for MPFI.

[Jeep Driver]

 

 

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

The MPFI 2.5L yes, not the TBI 2.5L. Theyre both EV1 style 19lb hr injectors. The trick in switching injectors is to find one that mists the fuel instead of just spraying it. Think of it like the dual spray pattern on a bottle of Lysol, 409 or whatever kitchen cleaner you use. Now one setting is just a stream, the other is more of a conical spray. Now air and fuel need to mix evenly for a better, more efficient burn. So which pattern do you think would be best if you shot fuel outta that cleaner bottle? The conical pattern because the fuel is a finer mixture than if it just shot out like a stream.

As for the duty cycle of an injector opposed to it's flow rating, take the 19lb number, this is how much fuel the injector will push if the needle is held constantly open. This is where duty cycle is used. Duty cycle is the amount/length of time the needle in the injector is held open by the ECU. The injector, much like the VE of a carb, never sees 100% of it's duty cycle so the 19lb unit operates more like a 15-16lb unit.

By switching to lets say a Cobra 24lb injector, you may gain a little more pressure for that brief cycle but the ECU still operates at it's pre-programmed duty cycle.

 

When you adjust things like MAP, O2, Temperature Sensors, etc, the ECU makes fine adjustments to it's duty cycle to adjust the A/F ratios. This is where the slightly larger flow rate helps out because the larger injector doesn't have to work as hard to flow more fuel.

 

Sorry for the lengthy reply, I'm just trying to awnser/explain your question as simple as I can for you.

 

I appreciate your response and I seemingly understand a little better.

 

To be specific though-

 

The 305 Chevy two barrel TBI uses the same style injector as does my 2.5.......that is what I was referring too.

[outlaw star]

 

 

 

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

The MPFI 2.5L yes, not the TBI 2.5L. Theyre both EV1 style 19lb hr injectors. The trick in switching injectors is to find one that mists the fuel instead of just spraying it. Think of it like the dual spray pattern on a bottle of Lysol, 409 or whatever kitchen cleaner you use. Now one setting is just a stream, the other is more of a conical spray. Now air and fuel need to mix evenly for a better, more efficient burn. So which pattern do you think would be best if you shot fuel outta that cleaner bottle? The conical pattern because the fuel is a finer mixture than if it just shot out like a stream.

As for the duty cycle of an injector opposed to it's flow rating, take the 19lb number, this is how much fuel the injector will push if the needle is held constantly open. This is where duty cycle is used. Duty cycle is the amount/length of time the needle in the injector is held open by the ECU. The injector, much like the VE of a carb, never sees 100% of it's duty cycle so the 19lb unit operates more like a 15-16lb unit.

By switching to lets say a Cobra 24lb injector, you may gain a little more pressure for that brief cycle but the ECU still operates at it's pre-programmed duty cycle.

 

When you adjust things like MAP, O2, Temperature Sensors, etc, the ECU makes fine adjustments to it's duty cycle to adjust the A/F ratios. This is where the slightly larger flow rate helps out because the larger injector doesn't have to work as hard to flow more fuel.

 

Sorry for the lengthy reply, I'm just trying to awnser/explain your question as simple as I can for you.

I appreciate your response and I seemingly understand a little better.

 

To be specific though-

 

The 305 Chevy two barrel TBI uses the same style injector as does my 2.5.......that is what I was referring too.

Ooops! Lol

[Jeep Driver]

 

 

 

 

 

Altitude compensation is done by the MAP.

 

The injectors are not running near their capacity as they are and there's plenty of "headroom" should more fuel be requested.

Yes this is true. Swapping injectors is for flow/spray pattern only. Injectors have what's called a "duty cycle" which is controlled by the ECU. Only way to get more flow from the injector is to tweak/program the ECU.

So, based on your stated logic-

 

An injector from 305 Chevy will deliver the exact amount of fuel as will the injector in my 2.5?

The MPFI 2.5L yes, not the TBI 2.5L. Theyre both EV1 style 19lb hr injectors. The trick in switching injectors is to find one that mists the fuel instead of just spraying it. Think of it like the dual spray pattern on a bottle of Lysol, 409 or whatever kitchen cleaner you use. Now one setting is just a stream, the other is more of a conical spray. Now air and fuel need to mix evenly for a better, more efficient burn. So which pattern do you think would be best if you shot fuel outta that cleaner bottle? The conical pattern because the fuel is a finer mixture than if it just shot out like a stream.

As for the duty cycle of an injector opposed to it's flow rating, take the 19lb number, this is how much fuel the injector will push if the needle is held constantly open. This is where duty cycle is used. Duty cycle is the amount/length of time the needle in the injector is held open by the ECU. The injector, much like the VE of a carb, never sees 100% of it's duty cycle so the 19lb unit operates more like a 15-16lb unit.

By switching to lets say a Cobra 24lb injector, you may gain a little more pressure for that brief cycle but the ECU still operates at it's pre-programmed duty cycle.

 

When you adjust things like MAP, O2, Temperature Sensors, etc, the ECU makes fine adjustments to it's duty cycle to adjust the A/F ratios. This is where the slightly larger flow rate helps out because the larger injector doesn't have to work as hard to flow more fuel.

 

Sorry for the lengthy reply, I'm just trying to awnser/explain your question as simple as I can for you.

I appreciate your response and I seemingly understand a little better.

 

To be specific though-

 

The 305 Chevy two barrel TBI uses the same style injector as does my 2.5.......that is what I was referring too.

Ooops! Lol

 

Met me ask you this way-

 

Assume the two injectors are the same......a single generic injector.....

 

Would they build or program the ECU around the injector?

[cruiser54]

They might. Based on flow rate needed for the engine at WOT and the 80% rule. 

 

The pulse from the ECU has to be able to REDUCE the fuel flow at idle/low speed enough that it passes emissions. 

[Eagle]

Snake oil

Yep. They were snake oil when they were sold for carburetors. Considering that multi-port injection squirts the fuel into the combustion chamber, and the air flow into the chamber is controlled by the intake valve, it is essentially impossible for these gadgets to have any real effect aside from lightening the owner's bank account.

[johnj92131]

According to some reading I have been doing on different stroker sites:  The throttle body spacer is supposed to change the length of the intake manifold path.  On the 91+ H.O. manifold the runner length is something like 11 inches, on the 99+ it is something like 13.5 inches and longer runners are supposed to aid low end torque production.  Notice I said "supposed" several times.  Also the 99+ manifold runners are smaller in cross section than the H.O. manifold.  That also aids low end torque and is supposed to provide a higher air velocity.  As for the spacers You have to ask yourself - if it was that simple, why didn't the factory do it?

[cruiser54]

According to some reading I have been doing on different stroker sites:  The throttle body spacer is supposed to change the length of the intake manifold path.  On the 91+ H.O. manifold the runner length is something like 11 inches, on the 99+ it is something like 13.5 inches and longer runners are supposed to aid low end torque production.  Notice I said "supposed" several times.  Also the 99+ manifold runners are smaller in cross section than the H.O. manifold.  That also aids low end torque and is supposed to provide a higher air velocity.  As for the spacers You have to ask yourself - if it was that simple, why didn't the factory do it?

Yep. 

[HOrnbrod]

All I can do is respond to what worked for me. All the above applies to Renix stuff it seems, except for John's post above. With a stroker, with a 99+ intake manifold, and with a 62mm throttle body to match the manifold, all was well. Picked up a Hesco 62mm throttle body spacer, installed it, and had tranny late shifting problems due to the bend the TV and accelerator cables had to make with the valve cover cable guide at it's stock location. When I raised the cable guide guide up 1" off the valve cover to match the height of the spacer, everything was super smooth after the ECU relearned. It quieted down the too quick throttle response, smoothed the shift points, and improved idle a lot. It's time for another dyno run at Hesco since I've done quite a few mods since the last run, and I expect to see some slight improvement. Particularly if the new 96 throttle body mounted MAP provides the same outputs to the ECU over the RPM range.

 

Getting back to the OP's question, the answer is no, a TB spacer will do nothing harmful or gainful for an NA Renix. Not much of anything else will either.  :yes:

[cruiser54]

I will disagree with the last statement. There are gains to be had with a Renix from an advanced CPS, indexed distributor, 60mm throttle body, and eliminating the "crush" in the downpipe. The addition of an HO exhaust manifold will add some more gain. 

[HOrnbrod]

Minor gains at best mate.