areXseven

iTrader: (1)

Well let's get one thing straight!!!. I stopped wearing panties many years ago. I like the "tubeless" feel

I agree with your previous comment that a stock FD can, or should do, 140 mph in 4th gear. He was only doing 11 miles less ( and that was before he reached red-line).

The additional 30 mph top speed that you refer to doesn't apply till you're in 5th, at or near red-line.

Anyway,..you're right,..no reason to go to the mattresses. Thanks.

rynberg

marix1521

k, thanks guys. I'll be sure to order a boost guage asap. I already planned on getting one so i could monitor it, but now i really need it to see what's wrong.

Now then.... Where should i locate it? Steering column, A pillar, center channel? *shrugs*where do you guys have it and what do you think is the most comfortable?

SiKoPaThX

iTrader: (2)

get your boost gauge and only your boost gauge on the a pillar, anything else stick in the center channel.

-god

Sgtblue

iTrader: (16)

Uhhhh, YEAH! And with a friend in the car no less.
Thought I was loosing it and was the only one.

FDNewbie

iTrader: (10)

I don't get 2 things...

- If 4th gear ends at right about 140, and the stock top speed is 157ish, 5th gear is only good for 17 mph?? That seems retarded to me (although it may very well be true. I just find it kinda shocking). For every gear on the FD, its around 40 mph! Do you lose THAT much top end power??

- Rynberg, you said boost leak is prob. most responsible for the loss of acceleration. My understanding of the turbo was to enhance/aid acceleration, but it's not the ONLY way to accelerate...

So technically speaking, even if your turbos went completely dead, wouldn't you still continue to accelerate, but just at a much slower rate?

rynberg

It's not retarded. 5th gear is there to provide quieter noise levels, less engine wear, and better fuel economy on the highway. Most American V8 cars reach their top speed in 5th, rather than 6th, because 6th is really overdriven to increase fuel economy.

Well, yeah, you would continue to accelerate until aerodynamic drag prevented you from accelerating. How much horsepower does the FD make with no boost? 160-180 hp most likely, which is about right to reach a top speed of around 130 mph. I'm not saying he doesn't have other issues but it is readily apparent he is not making much power.

FDNewbie

iTrader: (10)

I understand the highest gear is essentially an overdrive...but how it's more fuel economical, I don't understand.

I thought you get more fuel economy out of higher revs, but that comes at the expense of engine life...

And on the same token, when I'm in 5th on the highway, doing say, 80ish...the throttle response is horrid. I'd think I'm wasting incredible amounts of fuel to reach the desired speed vs. if I downshifted...which is essentially why I've driven in 5th maybe a handful of times... half cuz I was experimenting, and the other half cuz of the speed hehe

Oh and I totally understood your point about the top speed and aerodynamic drag. Good point.

marix1521

ordering my boost guage today.

5th gear will give you better gas milage because of lower RPM's, the less your motor is spinning, the less gas is being put into it, therefore less gas being used up. just because you have it floored doesnt mean that it's spraying loads of gas in, it just means it's opened up as much as it will go and is spraying the max ammount requested at that speed and RPM

EDIT: i also have no clue as to what vaccum lines go where. would ordering an aftermarket silicone hose kit be the best way to go? the hoses ARE 11 years old now and they could be getting ready to be replaced anyway

rynberg

Nope, not at all. Lower revs are much more fuel efficient.

Also, if your throttle response at 3000rpm in 5th is horrid, then something is either wrong with your car or you are running non-sequential...

novadan67

This is true to an extent. Obviously if you are going up a hill or trying to accelerate and your revs are very low you will be better off shifting down. Watch your boost / vacuum gauge, it will tell you a lot about how much fuel you are using. In general, the higher the vacuum, the better the gas mileage.

novadan67

It is my understanding (I have not experienced it first hand) that the stock FD's speed is horsepower limited, not gear limited. Meaning that at 160 you do not have enough hp to go any faster (due to wind resistance), but you do have more rpms before redline. That being true, if more power is added, 5th gear will be good for more than 17mph.

FDNewbie

iTrader: (10)

Rynberg, what novadan67 said is what I was referring to.

If I'm driving along in 5th, and I'm trying to overtake someone, I can give it WOT, it'll reach full boost, and the response is sluggish compared to if I downshifted. In my mind, I'd think that means it's giving much more fuel at that point than it would if I was in 4th, 1000 rpms higher, but boosting much less to accelerate to the same speed. Does that make sense at all?

I'm not saying it's correct, but the way I'm thinking about it applies to almost any gear that isn't optimum for your speed. I'd think in that case you'll have a sluggish response and bad fuel economy, since you're gonna be boosting higher and for longer to get the same result.

alberto_mg

Refer to the newbie stickers for various writeups on installing boost gauges. Its not that hard but a good first project for someone with a 7. just be careful not to pop off other hoses while you are doing it.

As for replacing the vacuum hoses with silicon, yes that is a good idea. But its not a job for someone new to the FD. Research it a bit and you'll see why.

FstFD3SPOWER

i have same problem... mine aint stock though..


i think im just running too damn rich
.

Swolbynos

5th is more efficient at a CRUISING speed, not accelleration, so yes you would get better economy by downshifting, also less load on the combustion chamber.

maxcooper

To a certain extent, the rate at which you are accelerating determines your fuel economy. I used to think that downshifting would put you at an RPM at which the engine was more efficient and thus offset the negative effects of running at higher RPMs. However, watching my injector duty cycle during some downshift versus don't downshift experiments has led me to believe that you pretty much always get better fuel economy in a higher gear. Even in the case where you are lugging the car under boost versus using less or no boost in a lower gear. The higher gear seems to almost always give a lower injector duty cycle, which means better fuel economy since by definition the injectors are open a lower percentage of the time. Perhaps the lower gear catches up some by requiring less time to get to a speed, but you'll pretty much always be at a higher duty injector cycle (= burning more gas) in the process.

-Max

FDNewbie

iTrader: (10)

Swolbynos, you pretty much summed up what took me 2 paragraphs to say lol

Max, thanks for the explanation, and I understand exactly what you're saying. I gather from what you said that rpm is really the major basis for injector duty cycle, not boost. Hence why you always observed a lower injector duty cycle in the higher gear.

But at the risk of seeming stubborn (which honestly, I'm not trying to be...but I just wanna make sure I understand fully as well as that you see my point fully), give this idea a shot. The #s I'mma totally make up, simply to illustrate my point (that and I don't have enough technical knowledge to use accurate figures)

- You're in 4th gear, 4000 rpm, 80 mph. You're trying to hit 100mph. You give it WOT, injector duty cycle increases radically, and you accelerate.

Lets say you're delivering 500cc of fuel per second, and it takes you 6 seconds to reach 100mph. 500cc/sec X 6 seconds gives you 3,000cc of fuel consumed to achieve your goal.

Now try this scenario.

- You're in 5th gear, 3000 rpm, 80 mph. Same goal: You're trying to hit 100mph. At WOT, injector duty is much lower than it was at 4th gear, since the rpms are lower. Lets say you're only delivering 300cc of fuel per second. But since this isn't the optimum gear, it takes you 12 seconds to reach 100mph. At 300cc/sec X 12 sec = 3,600cc of fuel consumed to achieve your goal.

Hence, while your injector duty cycle was lower in 5th gear - and considerably lower at that, simply the amount of time it took you to reach your goal counteracted and even overcame the benefit of the lower duty cycle, ending up costing you more fuel, and hence worse fuel economy.

Feel free to tear my example apart, cuz I'm actually really trying to understand this. Just be nice about it...go easy on the newbie hehe

Oh, and all this is under the premise that I'm accelerating. We've already established that while cruising, 5th gear is definetly more fuel efficient.

Thanks
~Ramy

rynberg

But 5th gear is for fuel economy WHILE CRUISING. Who gives a **** what your gas mileage is when you are going WOT?

In any case, your example still doesn't work, except maybe in extreme circumstances. Large throttle openings at low rpms have been been proven to be more fuel efficient than smaller throttle openings at higher rpms, with any type of engine.

FDNewbie

iTrader: (10)

Gotcha. I guess the only reason I was factoring in acceleration was I really can't "cruise" at 85 or 90mph where I live...that's a court date and probably suspended license...so I end up drivin 80ish (lol...big compromise!)

Point is...I think that's right around 2800 - 3000 rpm in 5th...and if I wanna go ANY faster for any reason (overtake a car) or even maintain my speed up a hill, it sux. Period. So I essentially never use 5th for that reason.

rynberg

You should have ZERO problems maintaining speed on a hill or overtaking a car at 80 mph in 5th. I easily zip past traffic and up hills with just a nudge of the throttle. Are you getting proper boost?

adam c

iTrader: (2)

If you are trying to accelerate as quickly as possible, by definition, you will use more fuel. You won't use 5th instead of 4th, because the lower rpms will not accelerate the car as quickly.

If you cared what gas mileage you were getting, you wouldn't be at WOT

FDNewbie

iTrader: (10)

Adam, you're right, and I personally don't care about fuel economy. On a good day, it still sux lol. In fact, w/ the way I drive, on 94 octane mind you (Sunoco), I fill up every 2 or 3 drives (which last only about an hour or so lol). I push her HARD.

Rynberg, you're starting to make me doubt myself lol. I'mma hold off on this until I take my car out for a spin and try it again...but I think my memory is serving me right.

As for boost, I have the PFC programmed for 11 and 13 psi, and she works just fine at both boost levels.

clayne

No.

Air resistance and drag is an opposing force with an exponentially rising rate which you need more power to overcome.

clayne

Please stop the NS mis-information, thanks.