Good Morning,

I'm starting Day 3 with my HCH II, and I'm slowly learning the nuances of this car. The stop-and-go of Houston traffic has dragged my mpg's down from 52 to 46, but I'm sure that a little more time and practice will address that.

My big question is about acceleration. I've been reading the posts and elsewhere on the web, and I'm not clear on how to do it to minimize the fuel consumption penalty. From a dead stop, is it best to get the car to speed as quickly as possible (2.5-3k rpm) or to gradually get to the desired speed (1.5-2k rpm)? I've seen conflicting information on the web, and my tiny little brain can't handle the confusion!!!

If it's of any help, I'm finding that my cruising speeds are about 1k rpm in the city (at 35mph) and 2k rpm on the highway (at 65mph).

Thank yee,
Jeff

 

I've tried both myself and as soon as I think one way is better a different set of circumstances throws my theory right out the window. I suggest you try a mix because not one style will always work.

 

I accelerate slowly.

I am also confused by what I read.
I guess the only way to be sure is to do a good test.

Drive the exact same path both ways, accelerate hard or easy.
Do it several times, and average the results.

Make sure the car is warmed up.
Perhaps do 10 runs, alternating fast and slow.

 

Slow accleration is generaly best. Think of it this way. the power you need to move something increases when you increase the speed at which you want it to move.

 

I would say as slow as you can safely and not hinder traffic or drive you insane. I don't know about the 06, but with the instant guage, when feasable, I try to accelerate with assist at the highest possible mpg ... which is one bar shy of 40 mpg. I have found not a huge difference with accelerating between 20-30 mpg, but higher is always better, just think of h.s. and doing averages. If you accelerate at 20 mpg for 20 seconds, you will have to drive at 80 mpg for 20 seconds to maintain 50 mpg average. If it is 36 mpg, the you would only need 64 mpg on the glide side. I was trying to teach myself last night, but unfortunately it was 40 degrees outside, I didn't realize that until I got home. I could only sustain my speed/glide at around 60 mpg except for a few sections, but the few nights previously when it was around 70, I was able to keep it around 80 much easier. I still managed to raise my mpg from 52.6 to 53.3 with the hills, traffic, and coldness, I have about 320 miles on the tank. I don't know if it is a quirk of the HCH I, but I can get better mileage in the city with my personal technique. I drove mostly at between 45-55 mph, some of my pulse and glides took me to 60/65 and down to 40. I am planning to do this trip again when it is warmer. Oh, I also had my first forced regen, but it was at half charge, I thought it would be lower than that, but it still maintained 60 mpg.

So to put it simply, accelerating at 1500-2000 would be best, especially if you have lights and you utilize coast and regen. If you will be able to hold a high mpg for a long time, you can accelerate quicker if it pleases you and still achieve great mileage. But always put safety first, and drive how it will make you happy, it is your new car, no matter what you do, you get better mileage than 99% of the people driving similar.

I will pass the advice that xcel told me.
just switch HCH I for HCH II ... I am sure he would have the same thing to say to you ... and remember, you still have break-in time ... many have said the FE goes up several times in the first 10k and I think I read it will a few more times up to 30k miles.

If you can find out any new information on you tests please share! You may find something out that no one else has before

Take care and have fun!!!

 

I've never been able to do one or the other to any significant and/or consistent degree to know if makes a difference. I'd be willing to bet that most folks can't either, only because isolating all the driving variables to conduct a specific experiment is difficult to do. However accelerating slowly seems to be preferred.

When given the chance I'll accellerate at a modest rate. When I'm at speed I'll tend to use short, agressive bursts if I need a 10 MPH bump. Cruisng at steady speeds does more for me than anything.

Enjoy your car!

 

I had the same questions, so I did some experiments that you can read about in this thread. I was experimenting with pulse & glide and I wanted to know how hard to accelerate during the pulse for maximum FE overall. Here's a summary of the results (see the thread for more details). The MPG numbers were over a 5 mile segment.

This is a very specific test on a particular stretch of roads, so results in other conditions will vary, but I think it shows that there's a 'sweet spot' with regards to the rate of acceleration. Accelerate too hard and you use too much gas during the pulse. Accelerate too slowly and you actually use more gas overall because you spend more time accelerating, and cruise FE is always better than acceleration FE.

Of course, this completely depends on how much time you will spend in the cruise segment after you accelerate. The more time in cruise, the more time you have to 'make up' for the lower FE you got during the acceleration (slow or fast). This experiement was one extreme; there was no cruise, just a glide after the pulse, so the amount of time spent in the pulse was critical to overall FE. It does show, however, that slow acceleration is not always best, especially in city driving where you don't get to spend a lot of time in cruise mode. Think about it this way, if you accelerate so slowly that you never get up to cruising speed before you have to slow down again for the next light/traffic/whatever, you will spend most of your time below 40 MPG (at best) and your tank average will suffer.

 

You did not mention what speed was your top speed before you started your gliding. You did mention that if you didn't have enough glide or cruise time you wouldn't make up for the lower FE during acceleration. However, what if you lowered your rate of acceleration and started cruise earlier?

 

I was mostly doing P&G between 30-45 (check the referenced thread for all the details). Usually you have a target cruise speed in mind (speed limit, 5 below speed limit, whatever), so that's where you start your cruise. Your rate of acceleration just determines how long it takes you to get to that speed. There's a tradeoff between the mileage you get during the pulse (slow accel helps) and the amount of time spent during the pulse (slow accel hurts). There are many variables, but an acceleration rate between 2000-2500 RPM seems to work best for me (research in progress!).

 

I'm starting to be converted. I pretty much used the 2000RPM rule on the way home when I had at least a 1/4 mile until the next stop sign to allow me to get up to speed and hold it for a little bit. It seemed to work out. Hard to say though.