Reason why the I-force v8 doesn’t respond very well to engine modifications.

[v8Toilet]

After putting my truck on the dyno and also seeing Vanity Plates truck on the dyno with the exhaust gas analyzer I was very surprised to see what I saw. Group dyno run results Both our Tundra’s ran extremely rich! I have seen this before with another members truck were his air fuel ratio was ~11.0 to 1. With the TRD air filter and Spintech muffler my air fuel ratio was a way rich 10.0 to 1 or richer since that was as low as the analyzer went. When I put the stock exhaust back on and installed a regular paper filter my air fuel ratio returned to a more respectable 11.0 to 1 but it was still too rich. When Vanity Plates removed his air filter entirely his truck also went to a low 10.0 to 1 from 11.0 to 1.

I asked the Dyno owner and operator, Dean, why this is so. Dean said that the manufacturers design this on purpose for safety. Dean said that the computer reads the increased airflow through the MAF meter and doesn’t know what to do so as a safety it richens the mixture. This may be why the K&N filter has been so unsuccessful with the Toyota Tundra in terms of power. He said that many of the Mustangs are also doing the same thing. The overly rich mixture is costing me a lot of power and gas. Most engines develop the highest torque at ~12.5-13.0 to 1. Just about none of the other trucks that I saw run on the dyno ran that rich even with modifications. They also respond much better to modifications like exhaust systems and air filters. Even though my air fuel mixture was overly rich I still gained 13.22-ft. lbs. of torque and 3.27 horsepower with just the Spintech muffler and TRD air filter. This means that this I-force v8 would respond very well to simple modifications if the air fuel ratios didn’t go so rich.

I believe that the engine computer in the Tundra is the reason why modified Tundra’s aren’t producing the gains that they should be getting even when you allow time for the computer to adjust. Dean did say that if the Torque curve is flat enough that you could put on a fuel pressure regulator and lower the fuel pressure. This would not effect the air fuel ratio under normal driving but it would lean out the air fuel ratio under full throttle across the entire rpm range resulting in larger power gains from engine modifications. The better option would be to use some kind of piggy back computer like the Unichip to custom tune the air fuel ratio for more power under full throttle. The good thing about the Unichip also is that it has the ability to reduce fuel consumption under normal driving conditions and increase drivability as well.

[indecline]

you should read my post regarding "Help with Supercharger" - a mechanic at Ed Hanson's Muffler (a well respected and longtime performance muffler shop in San Diego) told me the exact same things you describe - he said that basically if you install a dual exhaust, larger tubing, cat back systems, or even just a straight-through muffler (as opposed to a chambered muffler) it will throw off the aft-cat O2 sensors - this is generally true with all OBDII emissions vehicles - the extra flow of air causes the sensors to signal the engine computer to richen the mixture, therefore robbing your vehicle of torque/gas mileage/HP. There is a reason that the engineers designed the system the way they did - backpressure plays a very vital role in engine performance - I'm sure that if HP gains were so easily attainable by simple exhaust mods - the engineers would've included them in the original design of the vehicle.

As for the K&N, he explained to me that the FIPKs obviously suck in way too much hot air - sitting right in the engine compartment - causing the sensors to richen the mixture as the hot air is heavier - therfore loss of torque/etc - as far as the drop-in K&Ns - he said those were ok...why, I don't know - but he said the computer would properly adjust within a few minutes - I didn't think to ask why...

This is why I believe the s/c is one of the only viable (albeit damn expensive) mods available for the Tundra - esp. for the 2003 - which won't have a TRD header

[arkie6]

Where did the dyno operator measure the Air/Fuel ratio? From a probe in the exhaust tailpipe or tapped into one of the stock front O2 sensors? From what I have read on the BMW boards, measuring A/F ratios downstream of the catalytic converters is not very accurate.

From what I have read, primarily on the BWM boards, the problem with performance modifications on late model cars is due to OBDII adaption. 95 BMW M3s with OBDI respond quite favorably to intake, engine, and exhaust modifications. 96+ M3s with OBDII electronics are lucky to get 10-15 HP out of the same mods that I can get 25-30 HP from in my OBDI M3. In fact, one of the performance paths that 96+ M3 owners pursue is to switch all of the electronics over to the older OBDI (rather expensive, time consuming, and not legal).

It is almost like OBDII knows how much horsepower your engine needs to move your vehicle and adapts to that in an attempt to reduce emissions. After I have pulled my 18' fiberglass bass boat or 16' utility trailer loaded down for 20+ miles, my truck feels like it picks up 25+ horsepower for the first 5 miles after I unhook the trailers. After 5 or 10 miles, performance is back to normal. Somebody needs to get some baseline dyno or 1/4 mile times down, then pull a 3000+ pound trailer around for a day, then immediately put the truck on the dyno/track to see what kind of gains were made. I bet they would be significant.

[Dude Boy]

Yellbird and I both have JBA's and Bassani duals with the 2 1/2" pipes. I've never dynoed mine but Yellbird did, and got about 220-221 HP. I think he had Borla's on before and didn't pick up as much gain as he hoped when he put on the Bassani exhaust.
He also reported very rich mixtures on the order of 10 or 11:1 under load.

I've felt that my Bassani exhaust probably hurt the low end but gave more power up high. After putting on the duals I ran some G-Tech tests that showed about 7.8 - 8.0 seconds for 0-60 MPH. This was pretty close to what Motor Trend got on one of their early tests of a stock Tundra, so I was fairly satisfied. Those G-Tech tests were made at about 400 feet elevation and 45 degrees outside temperature.

I put the headers on last fall and they seemed to make a little seat-of-the-pants difference, but not as much as I had hoped. The engine did seem pretty "eager to run" in normal driving once the tach hit about 2000-2500 RPM. The problem for me is that my tach is sitting at 1500-2000 in my usual style of driving.

I hadn't made any G-Tech tests of acceleration since putting the duals on a little over two years ago. Tonight I decided to go find a level stretch of road and try some 0-60 runs. The outside temperature was 60 degrees. I made (3) runs over the same stretch of road and tried both directions. I got a best of 7.44 and a worst of 7.61. The other time was 7.52 seconds. On the way home, I stopped and ran a 0-60 pass on an uphill stretch where I had previously tested and ran 8.22. This time I got 7.91 run. My Tundra weighs 4900 lbs with driver. G-Tech can be off plus or minus a tenth according to the literature that came with it.

Question for V8 Toilet if you are reading this; will your drag race program estimate what RWHP would be required to accelerate a 4900 lb. pickup from 0-60 MPH in 7.5 seconds? It's possible I'm getting something around 220 HP, same as Yellbird. This thing runs better than I thought it would, but I bet it would feel awfully slow on a dragstrip without all those rural telephone poles rushing by!

[speed25]

Arkie, that's interesting. I've always felt the same way after towing, but wrote it off as "well, I just got rid of the trailer!" But you're right. It always seems to me that it feels overly strong immediately following extended towing, then goes back to normal over time.

Maybe I'll ride my bicycle with the brakes on so I'll be faster when they're off!

[03TundraTRD]

V8 have you tried the Apexi Super AFC to change the air fuel ratio
I here alot of good things about this product(but only if you need to adjust the fuel tunning)

[v8Toilet]

Good answers! I'll get back to this when I have a chance.

[v8Toilet]

The dyno shop used an expensive machine with a wide band O2 sensor. He put a probe into the exhaust tail pipe just like he did with the other trucks. If the probe wasn't in the tailpipe correctly it could only pick up more oxygen and it would show a lean condition. My truck showed the richest mixture there. All the Chevy engines were around 12.8 under WOT. I did give the engine about 160 miles for the computer to adjust. Vanity plates Tundra had thousands of miles to adjust and his was a very rich 11.0 to 1. Still too rich!

The dyno operator did comment on the smell. It sis smell like a rich exhaust but I didn’t see any black smoke. That is a good question and I think I will drive down there and ask him that. Maybe the catalytic converters are so efficient that they are able to burn it off.

Yeah I know it is a cut and Paste from similar post but they are the same questions you know.

You would need 260 horsepower and 335-ft. lbs. of torque at accelerate a 4900 lbs. Tundra to 60 in 7.5 seconds with the four speed transmission and 3.91 gears with stock 265/70 R16 tires.

I never tried the Apex Super AFC. I’ve heard of it but I don’t know much about that one.

I’m going to try an adjustable fuel pressure regulator since the torque curve is so flat.

[Dude Boy]

You would need 260 horsepower and 335-ft. lbs. of torque to accelerate a 4900 lbs. Tundra to 60 in 7.5 seconds with the four speed transmission and 3.91 gears with stock 265/70 R16 tires.

V8 Toilet:

That must be about where I'm at. You are probably talking flywheel HP here rather that Rear Wheel HP though, right? A 15 HP gain over the stock 245 HP, along with 20 ft-lbs over the stock 315 ft-lbs sounds believable to me. All I can say is, it doesn't come cheap, does it? For me that figures out to be about $60 for each hp gained. I'm attaching a file showing one of Yellbird's dyno graphs so that you can see how rich his ran under those conditions.

Thanks!

Bob

[indecline]

Yes, he is talking flywheel HP - I have seen various numbers from different sources and the stock 4.7L Tundra's RWHP ranging from 180 to 220 - give or take certain tolerances/conditions I would say right around 210 or so is a safe bet for RWHP on a stock 4.7L.

By the way - did the Bassani setup you had have a chambered muffler? Or was it straight thru like most of the Borla mufflers...how did it sound? Right now I have a FM and it gets quieter anything after 2500 RPM - to me it sounds like some kind of Sedan or family car when the thing is fully gased...How would you say the Bassani sounds compared to Borla?

thanks,

Jason

[Dude Boy]

Jason:

The muffler is actually pretty small. I think it's straight through other than it has an "x" in it. It's pretty loud just easing around town, but I think it's fairly quiet when you're on it. I've never heard it outside the truck except when my wife moved it around the driveway once. I've heard JadeSR5's sound clip of the Borla, and from inside the truck it sounds almost identical to mine. Sorry I can't give you a better idea.

Bob

[indecline]

thanks - my experience with Borlas on other cars has always been that they are very loud when you get on it - from what you said I'm getting the feeling that no matter what muffler is used, the catalytic converters and resonator (is there 2?) are deadening any kind of growl after 3K RPM - damn - to me it sounds like a floored 6 cylinder going up an on-ramp - and the FMs exactly as you describe the Bassani's - puttin around town it has a nice deep "tone" - but thats about it -

Without screwing up the backpressure I guess that's just the way it is...hopefully the whining of the s/c will divert my attention soon!!!!

[Mudog715]

Originally posted by v8Toilet
The dyno shop used an expensive machine with a wide band O2 sensor. He put a probe into the exhaust tail pipe just like he did with the other trucks. If the probe wasn't in the tailpipe correctly it could only pick up more oxygen and it would show a lean condition. My truck showed the richest mixture there. All the Chevy engines were around 12.8 under WOT. I did give the engine about 160 miles for the computer to adjust. Vanity plates Tundra had thousands of miles to adjust and his was a very rich 11.0 to 1. Still too rich!

The dyno operator did comment on the smell. It sis smell like a rich exhaust but I didn’t see any black smoke. That is a good question and I think I will drive down there and ask him that. Maybe the catalytic converters are so efficient that they are able to burn it off.
<snip>
I’m going to try an adjustable fuel pressure regulator since the torque curve is so flat.

Another thing to ask the guys at the shop: don't most of the domestic engines have air injection (usually into the middle of the 3-way cat after the engine warms up)? Wouldn't that extra fresh air being injected directly into the exhaust air stream "artificially" lean out the exhaust gas? Sure, some of the air will mix with the unburned fuel and complete combustion. But the air injection is not precisely calculated -- usually the system dumps more air than actually needed because there's no drawback to injecting too much.

The iForce doesn't use (or need) air injection to clean up its emissions. Wouldn't that account for the seemingly "rich" reading at the tailpipe? (BTW, The iForce doesn't have/need EGR either, another "bandaid" solution widely employed by the competion.)

(above cross-posted for your convenience)

Regarding leaning out the mixture by adjusting the fuel pressure:

1. I'd make DARN sure the mixture is in fact too rich before you lean it out. A new iForce short-block to replace the one you melted the melted pistons in from an excessively lean mixture isn't likely to covered by the 5/60 powertrain warranty.

2. Even if you do lean out the mixture at WOT with the FPR, I doubt it will have any long-term effect. I'm pretty sure the Tundra ECU extrapolates the fuel trim table it builds during normal driving to cover WOT operation as well. It no longer "fine tunes" with the feedback system at WOT, but I'm pretty sure it doesn't revert to the base fuel map, either. This means that the computer will just lengthen the pulse widths to compensate and the mixture will end up about the same. Only now, you have lessened the "reserve" provided by the extra fuel pressure.

3. When you look at the torque curve of the engine (240#ft@1,000, 275#ft@1,500, 290#ft@2,000, peak 315#ft@3,400rpm) that's a lot from a 4.7L motor. Compared to the other makes, the iForce is already in a high state of tune. The combustion chamber shape, intake & head flow, cam timing, spark control all seem to be pretty far ahead of the competions engines. The biggest flaw are the exhaust manifolds and replacing them IMHO provides about the biggest power improvement you're going to see short of: forced induction, nitrous, cam change or VVTi head swap. Switching out the exhaust won't make appreciably more power (torque), all it will do is move the torque curve up. The stock iForce torque curve actually drops quite fast after 4,000 rpm. Adding a big exhaust will extend this upwards a bit, at the expense of the torque below 2,500rpm. (Take the curve below and just shift the whole thing to the right. So what if you add 17 hp @ 5,000rpm -- how often does the engine see that? Was it worth it to lose 25#ft below 2,500rpm? Do you think the truck is faster now?) All the other things air intake, adj FPRs, Iridium plugs, etc. might bring a few extra ponies but it's hard to confirm because hp/tq readings from a chassis dyno are inconsistent. You can run the same vehicle (no changes) on two runs in a row and easily see a 5hp difference. So how do you know the 5hp from the <fill in the blank> came from the mod or it's just that was the "strong" run of the day? And on a nearly 4,700-5,000# (wet weight) truck, do you really believe you can feel a 5hp difference?

Doing comparisons of the "seat of the pants" feel between different vehicles is very inaccurate. Vehicles that have a well defined peak in the power curve, make more noise, or have lower gearing (rear end or transmission) will almost always feel faster, especially off the line. But that doesn't mean they are faster. A great example of this is my old Accord V6. It was lower geared than my Tundra, with a closer ratio automatic than the Tundra, had a strong power peak above 4,000rpm and the engine was a little louder. It felt WAY faster than my Tundra -- especially in 1st & 2nd gear. Well, it wasn't. Driven side-by-side, my Tundra would romp it off the line by half a car length, they'd then stay even until the Accord shifted to 2nd, then the Tundra would begin slowly pulling away again. The Accord would gain a little when the Tundra shifted to 2nd, but only briefly before the Tundra would continue to pull slightly away until about 80, then the Accord would begin catching up.

I'm sorry I'm not trying to be argumentative, just realistic. I get the feeling some of the people here have unrealistic expectations about what kind of gains they'll receive from the various performance mods. I also see people blaming various design features of the iForce (ETCS drive-by-wire, high-velocity intake/exhaust, tight mixture control, OBD-II, non-ambient referenced FPR, airbox restrictions, MAF restrictions, intake resonator, etc, etc.) for limiting the gains they receive from mods when the fact is many of these are responsible for the strong performace the iForce provides stock. Could it be that the Toyota really did get it right the first time and other designs, despite how superior they "appear" to be over stock, are actually inferior to the factory design?

I would even go so far as to say that I think it's pretty naive to think that the average "shade tree" engine tuner can out-do some of the best engineers in the automotive industry, with access to incredible amount of computer modeling capability. These engineers test literally thousands of engine combinations (intake, exhaust, cams, etc.) on the computer before they even build a test engine! Where you are going to improve over these engineers is on things that were either cost-dictated compromises or legislated compromises. Some examples of cost-dictated compromises are: the exhaust manifolds on the iForce, use of less agressive spark timing vs. requiring premium fuel, not using the VVTi heads on the iForce, not using 32-valves on the domestic V8s. Examples of a legistlated compromises would be the slightly lean mixture during part-throttle acceleration for cleaner emissions, the large, restrictive (but quiet) muffler stock mufflers, top-speed limiters (more of a insurance compromise).