How to Accelerate?
 

This is something that i have posted about a few times and find my self very conflicted. I have seen the advice from Wayne to accel slowly and then once up to speed and your are ready to Fas the to pulse at higher lod to get back to your target speed. The higher lod during pulsing i don't have a problem with.

I have a 2000 Honda civic hatchback that is almost gutted on the interior i have a carbon kevlar hood so my weight is def below average civics, and its 5spd, my tires are at 70psi and lastly the car has a full lower grille block which is on the inside of the grille which im not sure is causing problems or not? Right now according to my scangauge I am doing 60.3 MPG for the tank which is awesome, but for some reason i feel like I can do better.

So how should we accelerate, what rpm,lod and Tps ? For me i try to do about 65-76 lod but that is only like 25-30 at most on Tps , thats when I pulse after fas'ing.
What about when we are coming from a stop or just getting up to your speed where you want to start fas'ing?

Not sure if I am leaving something about but I drive slowly up to speed and its working but have seen some people with different results contray to what i am doing???

so whats the concensus??? Let the Great Debate Begin

David

Here's my take with the old set up on the crx: crxMPG - Gas mileage never looked so good » Acceleration and Fuel Economy Tested

I guess my results disagree with wayne's...but according to a lot of people he's god so we should ignore everything else! :D

That is a very interesting read SVOboy. I figured slow and steady was the way to go, but Jack rabbit while EOC won out. I need to try this some time, makes sense more time to coast with a fast pulse up and long coast down.

I plan on redoing the test with the new engine in, that's about two years old, but I was pretty meticulous so I trust the results.

What kind of tires are those, semi retreads. 70psi that is crazy. Must be good tires to hold that kinda pressure.

SVOboy, it was your post that i had read and had seen a few other people have the same results. which keeps me thinking but also the frugal person i am i don't want to go out and waste gas.

I am wondering if from the more rapid acceleration what my values on my scangauge should be, as in should i accelerate at 75 on the tps or with say 75 on lod? i know its different for everyone and one prob is i don't drive my car really at all during the week since i try to bkie everywhere i go locally.


My tires...well from people such as wayne and others one here and cleanmpg.com and from my research 70psi really isn't that crazy, especially from the research i had done on what it really takes to blow up a tire.

If you want better mileage, longer tread life, and a better handling car keep your tires psi high. Start at max sidewall psi and go up in small increments till about 70 some people have done more but thats where im at right now.

If you have a SG, just do a little testing! I doubt you'll ever find the ideal, but at least get a good idea and stick with it.

Whoa, 60mpg in a Civ? Nice! But I am a bit concerned with the 70psi tires as well. I mean, that puts the HYPER in hypermiling.

(I drive an automatic so I'm not sure how much you may get out of the followin...)

As for accelerating I was doing slow-n-go since driver's ed but I (finally) realized I was getting killed on the FE just to make my gears shift (I'm in an automatic). First heard about BSFC maps here and was intrigued. Got into the habit of accelerating around 70-75 load once I had my scangauge and I have noticed some differences especially in immediate MPG. The same stretch of road that I usually got 36-37mpg on, I started to see 39-40mpg once I did some load pedalling. Slow and go is good in general, but if you have the tools to see how far (and how hard) to gas, I say go for it.

Once I get to my ideal gear, my preferred settings are:

TPS: 15-16
RPM: < 2000
MPH: 40-50

At highway speeds, this has been my better configuration:

TPS: 16-17
RPM: < 2500
MPH: 50-55

I am not doubting you, but my brothers valve stems blew apart at the seams at 60psi. Just be safe no life is worth 1-2 mpg. Just my .02 not trying to be a tool.

I'll agree...exceeding the maximum by over 50% is pretty foolish. You wouldn't climb a 100 pound rated ladder to clean your gutters, would you?

i totally hear what you are saying but tires aren't rated for psi, manufactures put numbers on them to get certain parameters filled such as ride quality, noise and grip , which for me i want the least amount of energy wasted in my driveline and my tires to last as long as possible, heck i could have them at 30 psi like when my gf had some horrible perellis on her focus and the pieces of junk balloned the sidewall which were at manufactures reccomended specs.

so if something is proven to be wrong then i will stop but like our driving techniques someone told us all of these rules on how to drive when we were younger and find out now that most are not true , who am i not to try new things that have so far proven themselves completely true! I can see how somethings might be crazy but isn't that how most things are discovered or revolutionized? I am trying to think out of the box from the wasteful notions of my generations and generations past.

Well, just hope you don't hit a pothole. Bicycle tires are certainly different, but the same "suggested max inflation" things still come into play, and I've seen too many tires explode in races to take the same chance out on the road. Besides, by darin's coast down test, there's not even much difference in the rolling resistance.

I understand your point about questioning traditional wisdom, but when things like safety are concerned it's best to know first, and act second. Wayne will be in a world of sadness when someone hyperinflates, has a blowout, and then blames him for his completely uneducated recommendations. Unless he's secretly and engineer and knows more than the rest of us.

Back on topic. :p

I aim to always (regardless of speed) accelerate at around 80% load and keep rpms under 3000. With variations (rpm especially) from engine to engine, it is the most efficient way to accelerate, period. TPS doesn't really have much to do with it other than it effects load. One TPS reading will not work for everyone and will vary quite a large amount depending on many things. Load is the key.

I think there are benefit of accelerating slower. It allows you to not over-accelerate since you have more time to think and see what is going on. It also lowers average speed which will lead to small gains.

Moderate to brisk acceleration is most efficient. It operates the engine at its best BSFC (ie, maximum work for the least fuel).

Daox- your thoughts about slower acceleration are the ones i have been thinking that are contrary to accelerating briskly, and keeping the engine of best bsfc is what would make sense as well

Id have to say a scangauge or mpguino would really be the best way to tell. It really depends on the car, and the driving conditions. On my car, unless I really punch it, I get the same or better mpg with brisk acceration as with just spinning fluid at really slow acceleration (which I used to do before the mpguino). So getting up to speed faster is better since I get the same mpg for less distance.

I'm new to all this driving tech stuff, but brisk accel quite often leads to me using the brakes. I guess it just takes practice to judge correctly.

For me its not too much of an issue worrying about lights unless im in a completely unknown area which sometimes you really can't help but for the most part you can see it coming. Also when getting up to speed fsater will also mean that i can start fas'ing sooner and for longer periods of time which i think will really help along with keeping my target speed lower.

I use 30% TPS as my staple for acceleration, I was going to try 5% increases on following tanks but that never happened panned out because I stopped driving as much, so I just stick with 30% for acceleration and 13-15% for freeway cruising at 50-55mph.

A tuner informed me that honda's dont go into open loop unless throttle is over 90% and rpms are high enough.

I accel @ 0-1 in vacuum (about 75%) and always pulse from 1500-2000 rpm. This has given me high 60's in city driving.

Ha, I shift at 1500. :thumbup:

Shifting sooner is not necessarily better. It depends on the engine. Most engines are more fuel efficient around 2500 rpm.

Vince- i was hoping to hear from you, there was a post recently on ht where you had talked about your experiences and then seeing your employment with full race had the wheels turning wondering if you and the guys there had any crazy new parts that you have fabricated. I also seem to be folowing your recipe for my acceleration as well with the pulse and glide, sadly i don't regularly commute in my hatch so i haven't been able to hone my skills on a daily basis

based on that most efficient mean piston speed formula my optimal shift points are between 2000-2500.

2000 works for me, I still have a pretty good accel rate and that style of driving corresponds pretty well with my factory shift light.

It's pretty much ingrained in the way I drive, plus it lines up with the shift values recommended in the owners manual.

We always have crazy new parts and ideas :thumbup:

Its great working @ a fab shop like Full Race. I have access to some of the best tooling available and some of the smartest engineers I know. The best part is that the bossman is all for trying out new ideas and combining power with FE. I'm very lucky to say the least.

And trust me, ideas are flowing

here is a little teaser - Ive made a device that has low 50 degree output temps without the use of a AC compressor:thumbup:

well seeing the quality of work and your somewhat seemingly quick results speak for themselves which pair that with you have a civic very similar to mine makes me follow most of the stuff that you are doing. And any new stuff you need a guinea pig for or someone to do trial and error with im all for it. Im trying to understand more of the science behind how our motors work but its hard to keep up sometimes.

I will say keep up the awesome work , and let me know when you get the contraption for cooling ready i want a piece of that!

What do you mean by 80% load? I am just learning on this. How do you figure load %'s?

You get it from the scangauge. AFAIK it's the percentage of total available power (or is it torque?) for any given rpm you are currently using. Imagine the power curve in your head, the load is where you are in relation to the power curve (which is 100%).

which as posted above pretty means where you are closest to your optimum bsfc, i think thats correct. Also you can find out the load on you engine with a scangauge or using a vaccuum gauge

Yep, BSFC map is your friend in visualizing it.
I couldn't find one for my own car but I know there was a topic about them here. This is an article from Autospeed about them with a few example maps:

Brake Specific Fuel Consumption

1999 civic ex
 

I know I have the more powerful engine at 127hp vtec, but i find that while looking at my vacuum gauge the best vacuum occurs at 2500-3000 rpm, so you guys always talk about driving under 2k rpm but when i do in my civ vacuum remains low in or around 0-5 full throttle because it doesnt seem to have enough torque to move. what I'm asking is how to drive my civic in the city its a 5 speed so light throttle to get moving and coasting at 3000 to obatian best vacuum is this correct. I need a clear answer , most posts are a bit confusing please help.

well most cars are different but most of us with one of the d16 varieties have seen the best results staying between 1500 and 2500 at most but someone like me has gotten best results shifting at 2000rpm that way you also can keep your speed down easier, you just need to see what does best for you accel and shift at 2k, 2500, or 3k and then report back. Since i have a scangauge i use engine load which i keep at about 75

a
 

I can use the vacuum to see engine load, basicly lower the vacuum the more throttle im giving it, I would get a scan gauge but I find that they are too costly, the vacuum gauge was 20 bucks however on this tank with the spoiler removed new dist, 40 psi in the tires and grill block i think i am currently getting 36-40 mpg city

I get roughly 18-20in. hg. at idle and accelerate at 10in. on vacuum gauge where would that fall in load %'s. Just to give me an idea, I tried reading the link posted but got lost over my head I guess.

from what i have seen that you want too see the most amount of vac for the least amount of fuel used, higher vac means the throttle is closed hte most there for creating a vac in the intake manifold

Minimize pumping losses while accelerating.

Accel - least amount of vac without going into open loop
Cruise - highest amount of vacuum @ efficient rpm

imo

I like to accelerate at about 50% throttle at lower speeds, working up to about 80% at higher speeds and gears. Something like this:
1st gear: just to get moving. Shift before 5mph.
2nd gear: 50% throttle
3rd: 60% throttle
4th: 70% throttle
5th: 80% throttle pulse, then glide, then pulse again

Watching the scangauge, these throttle points roughly correlate to 70-80% load in each gear. At low speed and rpm, there's less power available, so it takes less throttle to reach the same load %.

80% load is about 12 on the MAP gauge, so near WOT but not quite there. I find that my Honda will go to Open Loop at about 90% load.

wow, thanks for putting it so simply
And i think i'd take your oppinion anyday because for a while there i was a tuner mag junkie and always loved the full race stuff. I don't generally "like" hondas but, well, you know, you work there.

i dont have any instrumentation (gauge cluster doesn't even work), but just driving my three speed tercel to work today with that little tidbit in the back of my mind, i think i've "modded" my technique for the better.

thanks for the insight.:thumbup:

so in watching lod on the scangauge you want 70-80% of the maximum out of your engine therefore keeping it in its maximum bsfc atleast that is where it would be for the honda guys here with the 1.6l engines