Gryphon problem.

04FX4 · #1 Wed, January 28th, 2009, 07:50 PM

I have noticed when driving real slow under 30 k my truck will hunt. It goes from 800rpm -1300rpm constantly and will not stop unless I let up on the gas pedal. Any thoughts? I also was wondering how much more HP a 2006 F150 has then my 04. The reason I ask is I know a guy who has the same truck as mine 2 years newer and no mods, and we have tried to see who's truck is faster. We start off the line about the same and eventually he pulls away from me, I would have thought I would have had the upper hand. He is running 87 fuel no nothing just stock. My truck has only 35000k his 58000 both are FX4 Screw same engine same everything, even same color,I cant figure this out.

Chris74 · #2 Wed, January 28th, 2009, 08:16 PM

I can't give you a proper technical answer for why your tranny is hunting at that speed..........odd

I'm sure Jack or Bill will figure that out for you but you may have to give more detail as to exactly what's happening.

As far as 04 vs. 06..........same horsepower and torque. Here's an important question for you though. Is your truck Canadian or American?......and what size are your wheels?
If your truck is Can. and you have 20" wheels........you automatically get a 3.55 gear ratio with 20" wheels!
If he only has 18" wheels.....then he would have a 3.73 gear ratio........and Yes - if you raced he would cover you with ease!

If this isn't the case......I have no explanation other than variation from truck to truck. But if both have 18" wheels and 3.73's and you are tuned and he isn't........something is really friggen wrong!

***Jackpine*** · #3 Wed, January 28th, 2009, 08:21 PM

Quote:

Originally Posted by 04FX4

I have noticed when driving real slow under 30 k my truck will hunt. It goes from 800rpm -1300rpm constantly and will not stop unless I let up on the gas pedal. Any thoughts? I also was wondering how much more HP a 2006 F150 has then my 04. The reason I ask is I know a guy who has the same truck as mine 2 years newer and no mods, and we have tried to see who's truck is faster. We start off the line about the same and eventually he pulls away from me, I would have thought I would have had the upper hand. He is running 87 fuel no nothing just stock. My truck has only 35000k his 58000 both are FX4 Screw same engine same everything, even same color,I cant figure this out.

The "hunting" problem sounds like something Bill might be able to fix. I've never experienced it in my 2005. It kind of sounds like a TC lock/unlock problem.

I imagine there were a FEW changes between 2004 and 2006 that might account for better performance from the later vehicle. Regardless, I bet if you put two identical trucks from the same year together and raced them, I think one of them(the same one) would always win. Manufacturing simply cannot produce true "clones". One is always going to be slightly better (or worse) than the other.

Oops! Chris - you snuck in on me and brought up a point I'd totally ignored!

04FX4's truck is TUNED! Yuk! Now the question is, what is the tune? It may not be set up for the race conditions described. And, yes, I would not have thought the '06s were improved that much over the 04's. But maybe.... 04FX4, have you looked at the HP Torque specs on these beasts from the two model years?

- Jack

04FX4 · #4 Wed, January 28th, 2009, 08:25 PM

We both have 3:73 gears and he actualy has bigger tires then I do as well. The only mod he had done was install the larger tires and front leveling kit. Should I wait for Bill to post or should I call him? Thanks

***Jackpine*** · #5 Wed, January 28th, 2009, 08:38 PM

Quote:

Originally Posted by 04FX4

We both have 3:73 gears and he actualy has bigger tires then I do as well. The only mod he had done was install the larger tires and front leveling kit. Should I wait for Bill to post or should I call him? Thanks

I think, and I can be dead wrong on this, that the larger tires are giving him the upper hand at high speeds. Assuming you both reach the same high end RPM, his tires are covering more ground with each revolution. And, he may not be hitting his rev limit as soon as you do. Smaller tires should give you an edge off the mark, but I think the larger tires will win out at cruise.

Now, everyone - tell me how full of **** I really am!

- Jack

04FX4 · #6 Wed, January 28th, 2009, 08:55 PM

I thought it took more HP and TQ to make the bigger tires turn. If that is true I should have the upper hand, but definitely do not.

04FX4 · #7 Wed, January 28th, 2009, 09:00 PM

I was thinking of calling Bill, but I know how busy he is maybe I will call him from work tomorrow.

***Jackpine*** · #8 Wed, January 28th, 2009, 09:33 PM

Quote:

Originally Posted by 04FX4

I thought it took more HP and TQ to make the bigger tires turn. If that is true I should have the upper hand, but definitely do not.

It does, but at high speed, your engine is turning over faster than the other guy's. You may be on the downside of the torque/HP curve at this point and he may be in the high region.

You SHOULD be able to pull away from him a bit at the start (of course you have to be careful not to spin the tires - he won't have as big a problem in this region with tire spinning).

And, I COULD be "full of it"!

(And it won't be the first time). :o Be interesting to hear what Bill has to say.

- Jack

***Power Hungry*** · #9 Thu, January 29th, 2009, 03:12 AM

The hunting should be easy to fix. Just a minor shifting inconsistency.

As for the performance, the 2006 may be rated the same for final output but the torque management strategy is completely different and results in a higher net output on the 2006 vs. the 2004. Also, the PCM uses load based calculations to determine how much power to actually produce so a slightly larger tire will actually translate into a slightly higher load and the PCM will let the engine produce a little bit more power.

To further illustrate this point, we had a customer that went to a shop that installed 4.88 gears in the truck thinking it would improve launch and acceleration. What ended up happening is that that load on the engine was so drastically reduced with the new gears that the truck ran slower than it did stock. Talk about an expensive mistake.

Because these calculations take place in the actual "program" or "software" part of the calibration, it is not something we can remove. We can change certain aspects of the output by modifying the throttle control mapping and other functions, but the fact remains that the less load there is on the vehicle the less power it will ultimately make.

I hope this make enough sense. In any event, we'll need to look into the shifting issue. Get with me tomorrow and we'll be happy to get it worked out

Take care.

kokopellimotorsports · #10 Thu, January 29th, 2009, 12:46 PM

So does the '05 F150 function like the '06 or the '04 in terms of load vs. power?