Question about timing, millage, and power

Hey all, I just received my new 13 DCLB MGM 4x4 TRD Sport Tacoma and so far couldn't be happier with it!! I studied about the truck on here for a couple months to decide what I wanted then went and pulled the trigger. Delt with the Sales Mang. direct at Sport City Toyota in Mesquite, he was a great guy to purchase from.

Now on the the question, who all has a scan gauge and watches the timing and millage while driving? I just received it along with several other mods in the mail today and got around a hundred miles under my belt driving with the new Scan Gauge II. I just found the timing to be very light and couldn't help but thinking thiers power and millage left on the table because of it? Im only running 93 octane gas in the truck and only interested in mods to improve millage not concerned with power it seems to run pleanty good to me with the little 4L V-6.

Running around in town at speeds say 45 and less, the timing is between 8-15-16* and out on the road with the cruise on 60 the timing may come up to 25-26*. I understand pre ignition has to be avoided but Id think most of the time Im looking at the timing for the givin' rpm and load Id think it was slow 10*. In short is their a tuner or computer that adds timing to the trucks base tuneup for improved millage gains?

I drag race and build my own engines so I understand timing and how it releates to torque at rpm under a given load. But maybe this being a alum headed hemi style combustion chamber its just more eff. and not require as much lead timing? Does anyone know, or track their millage close with a scan gauge? Thanks

Ryan

 

I got 16.9 on the first tank and 18.1 on the second. I had a small trailer in tow partially on both tanks. Now that I have the scan gauge on the truck I expect I will greatly improve that millage on the next full tank. It seems to be a great tool! Ive also purchased a ARE CX cap for the truck, it will be 7-10 days before it comes in. The place I bought it from says that many off his people claim 1-2 mpg increase from a topper in the Tacoma..... Id love to see that for sure.

Also the sticker in my drivers side door shows to run 28# of air in the tires so I looked on the tires them selfs to find they call for 51#. I aired them all up to that 51# and it seems noticeable to me so far, this next tank will tell. My plan is to never increase the size of the tire but go to a 10 ply when these are gone to get the 80# rating and super great wear like I ran on my 8k#+ dodge diesels, I got 100,000 miles on my factory 265/70/17 10 ply tires. The Taco at literaly half the weight should really last a long time! And at 80# of air psi posebly get better millage too.?.

 

The tires do not "call for 51psi", that's the max load and imo it's dangerous to run at the max and you'll wear out the center tread. Do the chalk test for best even wear, it'll be around 30psi.

 

It is not dangerous to run the max.
The tires were designed to be run that high.

The 51psi, in the complete sentence, is "MAXIMUM LOAD X,XXX AT 51PSI COLD"

That is the load capacity of the tire when inflated to 51psi.
The load capacity is reduced when the tire is inflated to less than 51psi.
The load capacity does not increase when the tire is inflated beyond 51psi.
It can be safe to run the tire above the sidewall pressure. I do not recommend it, simply because we don't know what the safe limit is, but hypermilers routinely run regular passenger car tires rated for 35psi at 50psi without problems.

I've been running my tires at or very close to the sidewall max for over 30 years and have NEVER ONCE worn a tire bald down the center.
40,000 miles on my BFG K/O's on my Duramax, aired up to 65psi for on-road, and they were worn perfectly evenly across the tread... probably would have gotten 100k out of those tires if I had kept the truck.... they showed very little wear at all.

Also, Navy tests at Pax River determined that the speed at which hydroplaning will begin is directly proportional to the inflation pressure. This is without regard to fancy tread patterns... they help very little. All that matters is that the tread depth is less than the depth of the water (any tire will hydroplane once the water is deeper than the tread).

"Speed (in knots) = 9 X the square root of the tire pressure (in psi.)"
"Speed (in mph) = 10.4 X the square root of the tire pressure (in psi.)"

28psi = 55mph
32psi = 59mph
50psi = 74mph

Contrary to common misinformation, higher inflation pressures INCREASE wet traction.

Higher inflation pressures extend tire life by reducing sidewall flex and tread squirm, which reduces tire heat. High speed driving with a tire underinflated can cause permanent damage to the carcass and lead to tread separation.

This reduced sidewall flex and tread squirm is also what reduces rolling resistance and improves gas mileage.

The manufacturer's recommended 28-30psi is a compromise between acceptable tire durability, fuel economy, and comfortable ride.
Yes, at sidewall pressure, your Tacoma is going to ride a little rough. It's a truck. It's not a Lexus.

 

Interesting read, thanks. I will leave them as they are for a tank to see, I find it odd that at now 490 miles on the truck that all 4 tires have their 'titties' still all the way across the tires. I tow a lot not super heavy but often, I will end up running the most I can with the best wear poss. what ever that ends up being. On my dodges I ran my 10 plys at max psi 80# for 100,000 miles with out a single issue, and I towed often and sometimes very heavy. The tires wear'ed unreal well, I may have rotated them 3 times in all those miles, and they all wore out very even.

I just know I got 18 mpg in my 1 Ton at 60# and 20.5 mpg at 80# so I see no reason that this 4200# truck wont do the same, but with the cost of tires being so high, I will keep a very close eye on wear exp. center wear as you mentioned and adjust as needed. Thanks

Ryan T

 

Rich, I typically agree w/ your contributions on TW but not this one. While underinflated tires are bad for lots of reasons, NHTSA did a study of 975,000+ tire related crashes and showed that vehicles with tires overinflated by 25% or more of the vehicle recommendation are twice as likely to be in a tire-related crash. Since the recommended tire pressure 28psi, going over 36psi would fall into this category.

From the NHTSA page 6: "of all the tires overinflated by more than 25 percent, about 7 percent were mounted on tirerelated crash vehicles. Figure 4 shows increasing percentages of underinflated or overinflated tires belonging to tire-related crash vehicles with increasing levels of underinflation or overinflation. Only 3.4 percent of the correctly inflated tires belonged to tire-related crash vehicles."

I won't paste the tables and graphs since Z-values aren't a popular conversation topic, but if anyone wants to read more: http://www-nrd.nhtsa.dot.gov/Pubs/811617.pdf

 

The problem with trucks is that the door placard is for the factory tire.
When you install a new tire, the same pressure recommendations may or may not apply.

The OEM tires on my 5-lug are rated for 35psi... so sidewall max would indeed fall within tolerance for the door placard 28-32.

But if I were to (as many do) install a set of load range "E" tires, the door placard would no longer apply, as those tires were designed to run at a much higher pressure.

 

Agree. I hope these suckers last a long time but when they do wear out, I guarantee I will switch to a heavy 10 ply tire. I've just been to impressed with them in the past. Michalens FWIW

It just makes since to me that less rolling resistance from more pressure is going to improve millage. Only thing is rather they have it in a 265/65/17 or not, my current 1 ton has 10 ply 265/70/17. I guess it wouldn't be a big deal to switch to that if needed, I'm sure that's not that much of a taller tire? The point is to improve millage not hurt it, I've read pleanty of crapy millage threads from guys going to taller tires......

 

Yikes... A 10 ply will probably outlast the truck.


And that's saying something given it's a Toyota


For tire size, here's a calculator to get you in the ballpark.
http://www.tacomaworld.com/forum/tirecalc.php

It's a double edged sword. You need to consider (and be honest) your usage.
If most of your driving is constant-speed highway on fairly flat terrain, then larger tires will save gas.

But for in-town, or mixed conditions, larger tires will hurt.
There's always the compromise of going to an 80+ series tire. Taller, but no wider, so it changes the final drive ratio, but has less impact on rolling resistance.

 

Wow, talking about a thread being hijacked! Very disrespectful.
OP, about the timing. I know of no program that will allow you to change the timing on these vehicles. Let us know if you find anything.

 

Ha, no worry's. Its all informative to me. And all relative to a increase in millage. To me the timing just flat seems low, I took the kids to school this morning and the timing never even got over 22*. Id just think that when in a light cruise mode with little to no load that timing up closer to 34-38* would offer a Big increase in low speed torque and increased millage. And then from there timing can be pulled by the computer to comp for load to keep the engine out of detonation. Its just a thought. Id never even had brought this up if not for the new scan gauge, because it runs and drives like a dream and not to upset so far with the millage as I think its going to be 20+ on this next tank, my question is simply: Is there some left on the table though just by adding a few degrees of lead timing??? I'd think so!

 

Thanks, that's a handy calculator. There's more of a diff. than I'd thought, an inch. basicly goes from a [30 10.50] to a [31 10.50]. With no more change than the asp ratio going from 65 to 70. Id also think that there'd be a chance that the millage could increase so long as thiers the power there to pull the increased taller gearing at road speed with out pulling down the engine. At that time if they offer the 10 ply in the factory size I will stay with it, if not I wont mind moving to the 265/70/17 to get the diff. in a tire that will last much longer.

 

Ok, well has anyone heard of this? Truck runs great and not fixing to jump out and spend money on this right now just curious if anyone has used it or something similar, strictly for millage.

http://www.gfchips.com/toyotatacoma.aspx

 

What made you bring NAS Pax up? We just rotated from there in DEC...

 

Gimmick....

I have a stock '08 v6 TRD with the off-road and towing packages and also have Firestone Destination A/T's on it. I am averaging right around 22 mpg (give or take - highest was 22.8, according to fuelly)...

 

Worthless. It just spoofs one or two of the sensors so the ECU changes the fuel trims, you end up running lean, which can increase the risk if preiginition from elevated head temperatures, which will trigger the knock sensor and the ECU will respond by backing off on the timing advance.

Credibility.

Last time this topic came up, one user in particular, and one other, got pretty nasty and insulting. I spent hours looking on the web for the formula and couldn't find a link to the testing.
A couple of weeks ago, I was cleaning out some old Excel files that I've had floating around since the Windows-3.1 days and stumbled across the formula.

 

A lot of guys are going "skinny"... moving to an 85 series tire with only a little more height.

Depending on usage, it's a good compromise. The narrower tread is better in snow and conditions where you don't need flotation. It also reduces contact with the road surface with reduces friction.
But it may be difficult to find an 85 series with a less aggressive tread pattern... a narrower aggressive off-road tread is going to have more friction than a wider street tread.

 

The ignition lead times have everything to do with how fast the mixture burns in the combustion chamber. Slow burning combustion is less efficient resulting in more unburned mixture out the tail pipe and requires more timing advance. The small lead numbers you cite for the 1gre mean that it has a fairly efficient combustion chamber with good swirl or turbulence.

 

Thanks again for the info Rich.

 

Ya I gathered the same theory after seeing for myself just how crazy slow the timing is on this engine. I towed last night to the races and was curious if it would be any diff. with the increased load, and as I fiqured it was less even again. Im not going to judge the Toyota engineering dept. as Im sure they did their homework and got the tune up close but Id love to be able to add 10* at a steady 65 mph cruise speed on the HWY and see what it did for millage. Im seeing mostly around 18-20* towing and maybe 25* empty at that speed. In any other engine that Ive built in the past Id be more in the neiborhood of 32-38* at a light load condition cruise, and then pull timing from there.