Modified Throttle Body....

[AmFam]

OK, I use to own a Sport Trac and was able to modify the T-Body. It made a substantial difference for small money input.

When I did the Sport Trac it was basically only $65.00 to modify the T-body. Once I ran it for a few months I was able to show the gains on paper. Increase of power as well as gas mileage as long as you kept your foot out of it..... LOL

What I did was shave the inside of the body out to make the outside wall 1mm thick. Built a new plate to fit the new hole, installed new screws to hold the plate on as the shaft is thinner. We obtained a gain of 70cfm.

I am looking to do the same thing on my RX300.

Here is how I did it for the Sport Trac's. I bought 6 used units from a salvage yard, sent them out to the shop, had the work done, then offered them for sale. With the Sport Trac I was able to sell them for $135.00

I checked with the local yards and the shop. Due to the cost of the used Throttle body and the shop labor and supplies the Lexus unit will be somewhere around $170.00 ish.

I am curious if others will have an interest in this. I just ordered one for myself to see if I can do the same as I did the Sport Tracs.

I will keep you posted on the results.

But I would like to know if others would be interested????

Thanks.

[wwest]

OK, I use to own a Sport Trac and was able to modify the T-Body. It made a substantial difference for small money input.

When I did the Sport Trac it was basically only $65.00 to modify the T-body. Once I ran it for a few months I was able to show the gains on paper. Increase of power as well as gas mileage as long as you kept your foot out of it..... LOL

What I did was shave the inside of the body out to make the outside wall 1mm thick. Built a new plate to fit the new hole, installed new screws to hold the plate on as the shaft is thinner. We obtained a gain of 70cfm.

I am looking to do the same thing on my RX300.

Here is how I did it for the Sport Trac's. I bought 6 used units from a salvage yard, sent them out to the shop, had the work done, then offered them for sale. With the Sport Trac I was able to sell them for $135.00

I checked with the local yards and the shop. Due to the cost of the used Throttle body and the shop labor and supplies the Lexus unit will be somewhere around $170.00 ish.

I am curious if others will have an interest in this. I just ordered one for myself to see if I can do the same as I did the Sport Tracs.

I will keep you posted on the results.

But I would like to know if others would be interested????

Thanks.

How did you compensate for the MAF/IAT sensor signals...??

The MAF measures the airflow at/near the center of the cross-sectional area of the throttle opening. The computation of actual intake airflow will therefore be based on the factory "as shipped" cross-sectional area of the throttle body. The result of your modification, seemingly, would be a leaning of the A/F mixture since more airflow is entering the intake manifold than the factory computation "predicts".

In any case I can't see that your mod would have any positive effect, if any, except at WOT where intake airflow would be limited were it not for you "mod". Same problem K&N has.

I suspect RX owners could obtain much the same effect with a simple 1/4 watt resistor (15 cents??) to modify the MAF/IAT signal.

[monarch]

How do tailpipe emission change? Cleaner or dirtier? In all driving conditions or just some conditions? Anything mod that increases emissions = degraded emission system component reliability and durability in the long run = degraded engine performance and fuel economy in the long run.

[AmFam]

Since I have not done this to my Lexus yet I can only go off of how it affected my Sport Trac.

If you drive normally the modification is a nominal thing. It is all relative as to how you drive. You will allow more air into the intake if you desire to.

By that I mean, if you are looking for some more lower end torque this is a good mod and did a good job for the money spent, compared to many of mods out there.

With my Trac I did get an additional .10 increase in mileage when I drove consistent with no heavy accelerations to speak of.

Where you physically felt it was if you pressed on the pedal and wanted some more umpf..

The Mass Air Flow Sensor was not affected as it did it's normal job. It communicated to the ECM/PCM and the fuel ratios were adjusted with no issues at all.

I live in a county that does requires EPA/AIMS testing. I passed every time, no issues.

Basically, it changes nothing until you want to have a bit more performance. It affects no sensors as they measure the flow and or volume just like they did before the modification.

I still need to look at the Lexus and measure the inside of the intake vs the Throttle body to see if the intake is smaller, the same size or larger. If ti is larger then it should be worth while as you will in fact get more air into the intake. On the Trac, it was the same size and it was still worth doing.

SO, I am going to see how it turns out and go from there.

On several occasions I had a Snap-On scanner on my OBED II to read all the data. It was all within range and never tripped any engine lights.

[golfinbud]

How did you compensate for the MAF/IAT sensor signals...??

The MAF measures the airflow at/near the center of the cross-sectional area of the throttle opening. The computation of actual intake airflow will therefore be based on the factory "as shipped" cross-sectional area of the throttle body. The result of your modification, seemingly, would be a leaning of the A/F mixture since more airflow is entering the intake manifold than the factory computation "predicts".

In any case I can't see that your mod would have any positive effect, if any, except at WOT where intake airflow would be limited were it not for you "mod". Same problem K&N has.

I suspect RX owners could obtain much the same effect with a simple 1/4 watt resistor (15 cents??) to modify the MAF/IAT signal.

Can you please elaborate on this 1/4 watt resistor mod? Thanks.

[wwest]

Since I have not done this to my Lexus yet I can only go off of how it affected my Sport Trac.

If you drive normally the modification is a nominal thing. It is all relative as to how you drive. You will allow more air into the intake if you desire to.

By that I mean, if you are looking for some more lower end torque this is a good mod and did a good job for the money spent, compared to many of mods out there.

With my Trac I did get an additional .10 increase in mileage when I drove consistent with no heavy accelerations to speak of.

Where you physically felt it was if you pressed on the pedal and wanted some more umpf..

The Mass Air Flow Sensor was not affected as it did it's normal job. It communicated to the ECM/PCM and the fuel ratios were adjusted with no issues at all.

I live in a county that does requires EPA/AIMS testing. I passed every time, no issues.

Basically, it changes nothing until you want to have a bit more performance. It affects no sensors as they measure the flow and or volume just like they did before the modification.

I still need to look at the Lexus and measure the inside of the intake vs the Throttle body to see if the intake is smaller, the same size or larger. If ti is larger then it should be worth while as you will in fact get more air into the intake. On the Trac, it was the same size and it was still worth doing.

SO, I am going to see how it turns out and go from there.

On several occasions I had a Snap-On scanner on my OBED II to read all the data. It was all within range and never tripped any engine lights.

When the engine is idling or operating at a relatively constant RPM, highway cruising at a relative constant speed, the front oxygen sensor, the one upstream of the catalytic converter, is the sole controlling factor for A/F mixture ratios. Above idle and during acceleration, engine under "load", the A/F mixture is enriched above the level wherein this oxygen sensor signal can be valid so control of the A/F mixture is now the result of the MAF/IAT module signal output.

At ~72F intake airflow temperature the IAT has a resistance of ~2000. Adding a 200 ohm 1/4 watt resister in series with the IAT signal, pin 4 or 5 of the connector, will make the engine/transaxle ECU compute the proper A/F mixture ratio based on a FALSE intake temperature. Adding the 200 Ohm resister will falsify the signal such that the computation will be made as if the intake air temperature is quite a bit COLDER (colder air is denser) than reality resulting in an inordinantly richer mixture, more HP/Torque (~5%), than was originally programmed at the factory.

Obviously boring out the throttle body will result in more air volume flowing into the intake manifold than the factory computation provided for at a given level of MAF signal voltage. Thus the factory computation would result in a somewhat leaner mixture during acceleration/engine "loading" situations. More fuel economy due to less HP/torque available for acceleration.

If FE is the goal then a 20k ohm resistor across the IAT signal wires will do the trick.

[golfinbud]

wwest,

have you tried using a resistor yourself & if so, how much fuel economy did you attain? also, what are the advantages and/or disadvantages of doing this modification? can you also specifically point out the 4 or 5 point location on the connector please. thanks.

[wwest]

wwest,

have you tried using a resistor yourself & if so, how much fuel economy did you attain? also, what are the advantages and/or disadvantages of doing this modification? can you also specifically point out the 4 or 5 point location on the connector please. thanks.

Experimentation was totally inconclusive.

I didn't dare, no "braves", do a falsification beyond ~10%. Since the effect seems to be only during acceleration or under pulling loads, times when the load-up clutch is disengaged, I wasn't surprised at not seeing any FE effects in either direction.

The truth can likely only be found on a dyno.

I don't think I would try to run lean in the long term and thereby (I suspect) put my catalytic converter at risk. On the other hand if one wanted a little extra BOOST then a slightly higher enrichment over OEM might not do any harm.

[TunedRX300]

Since I have not done this to my Lexus yet I can only go off of how it affected my Sport Trac.

If you drive normally the modification is a nominal thing. It is all relative as to how you drive. You will allow more air into the intake if you desire to.

By that I mean, if you are looking for some more lower end torque this is a good mod and did a good job for the money spent, compared to many of mods out there.

With my Trac I did get an additional .10 increase in mileage when I drove consistent with no heavy accelerations to speak of.

Where you physically felt it was if you pressed on the pedal and wanted some more umpf..

The Mass Air Flow Sensor was not affected as it did it's normal job. It communicated to the ECM/PCM and the fuel ratios were adjusted with no issues at all.

I live in a county that does requires EPA/AIMS testing. I passed every time, no issues.

Basically, it changes nothing until you want to have a bit more performance. It affects no sensors as they measure the flow and or volume just like they did before the modification.

I still need to look at the Lexus and measure the inside of the intake vs the Throttle body to see if the intake is smaller, the same size or larger. If ti is larger then it should be worth while as you will in fact get more air into the intake. On the Trac, it was the same size and it was still worth doing.

SO, I am going to see how it turns out and go from there.

On several occasions I had a Snap-On scanner on my OBED II to read all the data. It was all within range and never tripped any engine lights.

If you can provide dyno result of pre/post mod, I will be interested. The shop that perform the port and polishing, do they do benchflow?

[AmFam]

Well, with my Trac it was easy to provide the Dyno info. The man that runs the machine shop, (friend of mine that moved to Georgia) also owned a Trac. So I sent him one of the used T-boby's, he did the work and the dyno'ed his Trac pre and post.

The only way to do it with my Lexus is to spend the additional money and find a local shop. Not to say it is something I wouldn't do, just had not thought about it at this point.

I'll do some digging to see how much they will charge to do so.

[TunedRX300]

Well, with my Trac it was easy to provide the Dyno info. The man that runs the machine shop, (friend of mine that moved to Georgia) also owned a Trac. So I sent him one of the used T-boby's, he did the work and the dyno'ed his Trac pre and post.

The only way to do it with my Lexus is to spend the additional money and find a local shop. Not to say it is something I wouldn't do, just had not thought about it at this point.

I'll do some digging to see how much they will charge to do so.

Have you thought about port and polishing the intake manifold in addition to throttle body?

[wwest]

Well, with my Trac it was easy to provide the Dyno info. The man that runs the machine shop, (friend of mine that moved to Georgia) also owned a Trac. So I sent him one of the used T-boby's, he did the work and the dyno'ed his Trac pre and post.

The only way to do it with my Lexus is to spend the additional money and find a local shop. Not to say it is something I wouldn't do, just had not thought about it at this point.

I'll do some digging to see how much they will charge to do so.

Have you thought about port and polishing the intake manifold in addition to throttle body?

Reaming out, increasing the throttle bore, and/or polishing the throttle body will only be effective at WOT. Adding a 15 cent 1/4 watt 200 ohm resister in series with the IAT will add 10% to factory HP/torque anytime the engine is under pulling load, the torque converter lockup clutch is disabled.

400 ohms might even yeild 20%.

[TunedRX300]

Well, with my Trac it was easy to provide the Dyno info. The man that runs the machine shop, (friend of mine that moved to Georgia) also owned a Trac. So I sent him one of the used T-boby's, he did the work and the dyno'ed his Trac pre and post.

The only way to do it with my Lexus is to spend the additional money and find a local shop. Not to say it is something I wouldn't do, just had not thought about it at this point.

I'll do some digging to see how much they will charge to do so.

Have you thought about port and polishing the intake manifold in addition to throttle body?

Reaming out, increasing the throttle bore, and/or polishing the throttle body will only be effective at WOT. Adding a 15 cent 1/4 watt 200 ohm resister in series with the IAT will add 10% to factory HP/torque anytime the engine is under pulling load, the torque converter lockup clutch is disabled.

400 ohms might even yeild 20%.

Sorry I am not interested to fool ECU to think inlet air is cooler on a temporarily basis. I am interested either lower the real air temperature or increase flow. Not trying to debate because I know people will get real emotional. If someone can show me gain on the dyno chart, I am interested.

I do not agree/disagree with Pheonix's posting on this thread, just want to verify his claim of 25bhp gain by port and polishing on 1mzfe.

http://www.clublexus.com/forums/showthread.php?t=179583

[wwest]

Well, with my Trac it was easy to provide the Dyno info. The man that runs the machine shop, (friend of mine that moved to Georgia) also owned a Trac. So I sent him one of the used T-boby's, he did the work and the dyno'ed his Trac pre and post.

The only way to do it with my Lexus is to spend the additional money and find a local shop. Not to say it is something I wouldn't do, just had not thought about it at this point.

I'll do some digging to see how much they will charge to do so.

Have you thought about port and polishing the intake manifold in addition to throttle body?

Reaming out, increasing the throttle bore, and/or polishing the throttle body will only be effective at WOT. Adding a 15 cent 1/4 watt 200 ohm resister in series with the IAT will add 10% to factory HP/torque anytime the engine is under pulling load, the torque converter lockup clutch is disabled.

400 ohms might even yeild 20%.

Sorry I am not interested to fool ECU to think inlet air is cooler on a temporarily basis. I am interested either lower the real air temperature or increase flow. Not trying to debate because I know people will get real emotional. If someone can show me gain on the dyno chart, I am interested.

I do not agree/disagree with Pheonix's posting on this thread, just want to verify his claim of 25bhp gain by port and polishing on 1mzfe.

http://www.clublexus.com/forums/showthread.php?t=179583

"....not interested...." "...on a temporarily basis..."

"....I am interested...." "...or increase flow...."

Increased flow can only "happen" at WOT,.....on a temporary basis...at all other times the throttle plate is restricting flow beyond any measures you might add to improve flow. The very same problem K&N has, unless the throttle is wide open and the engine is near top RPM who cares if the OEM filter restricts the flow by ~7%.

So, if you leadfoot it a LOT, (hopefully only on the track) improved airflow will be of help. That's also why most race cars use K&N, enough time at or near WOT to make it count.

The aforementioned resistor would result in a richer mixture anytime the engine is under acceleration loads/loading.

[TunedRX300]

wwest, I think people will pay $ to see you and Pheonix argue to the ground on this mod. LOL.

I am just interested in dyno result because I believe the truth is somewhere between no real gain and 25bhp.

[wwest]

wwest, I think people will pay $ to see you and Pheonix argue to the ground on this mod. LOL.

I am just interested in dyno result because I believe the truth is somewhere between no real gain and 25bhp.

I don't doubt that providing more, and/or a "freer" intake airflow path would normally, certainly back in the days of carburation, result in a higher PEAK level of engine HP/torque. But then again I also know, am very certain, that the MAF/IAT module is there in the intake airflow path to provide a method of controlling the A/F mixture ratio when the engine is operating above the A/F mixture sensing capability of the upstream oxygen sensor.

The computational equation for this must be "fixed" at the factory based on the resistance to flow and the cross-sectional area of the intake at the point of measurement, at the MAF/IAT module. Think of it this way, in boring out the intake you are more or less, in effect, providing an air leak into the intake manifold.

Yes, more peak intake airflow, but with a resulting leaner mixture than the factory intended.

[TunedRX300]

wwest,

I believe MAF provide input to air inlet temperature and flow to the engine, A/F sensor provides input of exhaust air from the engine. ECU will use both sensor in a feedback loop fashion to finetune/map proper A/F ratio. Because air flow and what is actually achieve in the engine is very complicated, the process of determining a/f ratio has to be dynamic and quick in order to achieve optimum explosion.

Again, I am standing in neutral ground and not try to argue one way or another, just trying to find out about facts. That is why I kept asking about dyno results.

[wwest]

wwest, I think people will pay $ to see you and Pheonix argue to the ground on this mod. LOL.

I am just interested in dyno result because I believe the truth is somewhere between no real gain and 25bhp.

I don't doubt that providing more, and/or a "freer" intake airflow path would normally, certainly back in the days of carburation, result in a higher PEAK level of engine HP/torque. But then again I also know, am very certain, that the MAF/IAT module is there in the intake airflow path to provide a method of controlling the A/F mixture ratio when the engine is operating above the A/F mixture sensing capability of the upstream oxygen sensor.

The computational equation for this must be "fixed" at the factory based on the resistance to flow and the cross-sectional area of the intake at the point of measurement, at the MAF/IAT module. Think of it this way, in boring out the intake you are more or less, in effect, providing an air leak into the intake manifold.

Yes, more peak intake airflow, but with a resulting leaner mixture than the factory intended.

The oxygen sensor between the engine and catalytic converter is used to determine proper A/F mixture ratios insofar as lowest emissions are concerned. The oxygen sensor is like an on/off switch, function, it can be used to tell you that the exhaust has an oxygen content, not how much or high that oxygen content happens to be. The engine/transaxle ECU determines the proper ratio by slightly "dithering" the A/F mixture up and down in rapid sequence, resulting in the oxygen sensor output going "on and off" in the same sequence. If the oxygen sensor output doesn't "oscillate" in synchronization with the "dithering" rate of the A/F mixture then the ECU will go into "learn" mode in order to get the A/F mixture into the "sweet spot".

The problem arises when you ask the engine to produce an output power level which cannot be achieved while at the same time obtaining the lowest possible emissions level, the mixture must be enriched above the level desireable for lower emissions.

So, when you ask for acceleration the engine/transaxle ECU starts disregarding the A/F mixtuire oxygen sensor and begins controlling, enriching, the mixture based strictly on the MAF/IAT signal levels.

Bore out the idle air bypass "channel" and the system will quite quickly "learn" a new setting for the idle air bypass control solenoid. The same would be true of the overall intake path just as long as the system can use the proper A/F mixture resulting in the lowest emissions, say while cruising along on a level roadbed at a constant speed.

But once the need arises to enrich the mixture in order to produce the engine's peak HP rating the ECU will fall back on the factory default equation using the MAF/IAT signals only.

[TunedRX300]

wwest, getting off topic a little, but doesn't the voltage provided by a/f sensor indicates amount of O2 in the exhaust gas, it is a range of voltage readings, not just two values according to

http://www.lindertech.com/docs/j_thornton_...wraf_sensor.pdf

Attached is screen capture from p4.

Again I am not arguing with you, just want find out about facts.

[wwest]

wwest, getting off topic a little, but doesn't the voltage provided by a/f sensor indicates amount of O2 in the exhaust gas, it is a range of voltage readings, not just two values according to

http://www.lindertech.com/docs/j_thornton_...wraf_sensor.pdf

Attached is screen capture from p4.

Again I am not arguing with you, just want find out about facts.

Someone please step in and HELP if I am truly wrong.

It has always been my understanding that the lowest emissions are obtained when the A/F mixture is optimized to the point that virtually all fuel and oxygen is burned in the process of combustion. Therefore any detectable oxygen flowing past the A/F mixture controlling oxygen sensor would imply a "lean burn" mixture ratio.

Oh, maybe I see now....looked at your chart again.

I think, insofar as lowest emissions, the mixture should be in the range of 14.7:1, right in the middle of the A/F (oxygen) sensor signal range/resolution as shown in the chart. Again, someone correct me if this is wrong but isn't the A/F mixture desireable for peak HP, performance,in the range of 12:1 and above, just at the edge or slightly above the range of the A/F mixture sensor shown on the chart?

One of the charts via the link shows a vehicle accelerating, near or at WOT, to ~55MPH. During the acceleration it can be seen that the mixture is being enriched to the point that the A/F mixture (oxygen) sensor goes to the edge (0.512x5=2.560 volts) of its range/scale if not actually off-scale. Obviously it will be in the "region" wherein the MAF/IAT must be relied upon.

But what I find most interesting, REALLY INTERESTING, is the graph of the acceerator position as it goes from idle, fully released, to WOT in order to quickly accelerate up to 60MPH. The chart shows the pedal going slightly open, then closing completely, then to a more open position than before, back to idle again, and then finally to WOT. I cannot imagine a person "dithering", at least not intentionally, the gas pedal in the manner indicated.

I assume that this signal is sent to the OBD-II connector via the engine/transaxle ECU as a result of its sensing. A/D conersion, of the actual signal for the accelerator pedal absolute position sensors.

How many of you are aware of the numerous posts concerning inordinant transaxle downshift delays?

Talk about how to thoroughly confuse the engine/transaxle ECU's downshift firmware algorithm....!!

[wwest]

:chairshot: Oops, sorry, this can be deleted.

[TunedRX300]

Found a Toyota doc that explains very well:

O2 Sensors are mounted before cat, they just report lean/rich, however ECU uses it to finetune a/f ratio, A/F sensor is mounted after the cat, reports wide range value to monitor effeciency of the cat.

http://www.autoshop101.com/forms/h37.pdf

Flow dynamic is very complex, without bench flow, people who port and polishing actually lost hp.

from Porting FAQ on http://www.oflmotorsports.com/

Airflow:

The right way to improve airflow is to locate the best places to remove metal (or in some cases, to even add metal). This takes experience (knowing what kind of changes work and what doesn’t work), using the right equipment and/or tools (properly shaped cutters for reworking the various portions of the ports, valve pockets and manifold), and a flow bench to measure the changes in air flow produced by the various changes that have been made. The wrong way to go at it is to grab a die grinder and start hogging out the intake and exhaust ports with no idea of where you’re going or what you’re trying to accomplish other than to open up the ports. Bigger is not always better. Grind away too much metal and you may end up ruining the casting if you cut into a water jacket. But even if you don’t grind all the way through, removing metal in the wrong places can actually end up hurting airflow more than it helps. Here’s why: The secret to maximizing air flow and engine performance is maximizing volumetric efficiency and airflow velocity. Big ports with lots of volume will obviously flow more air than a smaller port with less volume — but only at higher rpm. A lot of people don’t know that. At lower rpm and mid-range, a smaller port actually flows more efficiently and delivers better torque and performance because the air moves through the port at higher speed. This helps push more air and fuel into the cylinder every time the valve opens. At higher rpm, the momentum of the air helps ram in more air, so a larger port can flow more air when the engine needs it. The ultimate port would actually be one with a variable cross-section that’s small at low rpm for high airflow velocity and gradually opens up for more airflow as engine speed increases. That’s sort of the idea behind staged split-plenum intake manifolds that open up and feed more air into the engine at higher rpm

.

I am going to wait for someone to dyno port and polish on throttle body and intake manifold, no sense to spend $ and risk to get nothing.