JamesS,

Sorry, I still don't buy it

Torque through the transmission isn't related to the rate of increase in revs - you could apply resistance, and the torque through the driveline would be at a maximum with no change in revs. And yes, my car will generate full boost in first gear and second gear.

I don't know about your car, but mine **definately** accelerates more quickly in 1st gear than 2nd, therefore the lower gearing causes more torque to be transmitted to the wheels than overcoming the inertia of the driveline cancels out. Did that come out right?

I would also doubt the wisdom of engineering the drivetrain with such a small safety margin that it was only barely capable of containing torque transients which are commonly encountered during normal operation. With the way these cars get driven, I think we would have a lot more transmission failure than we have had reported if this were the case.

Unfortunatly I think it is more likely to be an ECU 'feature' or peculiarity of the boost control mechanisms, especially given that some people have managed to have it fixed.

Cheers,

Alex

 

I placed a post on this page over 4 months ago which stated that I DID NOT have this problem. I even went out and tried to recreate it at the time but my car pulled strongly no matter what. My car has since developed this and I can now see why it causes so much annoyance. My point is that if the ECU is deliberatley designed to do this, why doesn't it happen on all cars? It's my guess ther is a component problem/mismatch because I didn't originall have a problem.

 

Alex_m,

30-50% of your tq is used to accelerate the driveline inertia in 1st gear - FACT defined by physics. When you accelerate from rest in 1st gear you are accelerating the vehicle mass against its load charateristic (called vehicle roadlaod) AND accelerating the internal inertia`s; conrods, crank, flywheel etc. This loss is greatest in 1st gear as the rate of acceleration is greatest here.

During a 5th gear accel, by contrast, you are accelerating the internal inertia`s much more slowly and so less energy is used doing this and more is passed direct to the transmission.

Tq into the transmission IS affected by the inertia in the engine/flywheel. However this is only a major factor in 1st gear.

1st gear is obviously shorter than 2nd therefore the tq at the wheel will be more in 1st than 2nd gear. The gearing effect being dominant over the inertia effects.

If you ran two cars side by side from rest the only differnce being low inertia engine/flywheel/clutch etc it would win easily - Why?

The difference would be greatest from rest and smallest in 5th gear.

This method is used in vehicles where 1st gear cannot deal with peak engine tq. ie rather than limit engine tq during a transient 1st gear accel (so the driver feels the engine isn`t pulling) there is a model of the driveline inertia`s in the ECU, it works out how much tq is being used to accelerate inertia`s and whats leftover to enter transmission; normally 1st gear engine tq is left alone.

During steady state manovers ie starting on a grade you are not trying to accelerate the inertias and more tq is transmitted through the transmission and hence engine tq may have to be limited.

I`m not saying the the Scoob is doing this but other vehicles do!

 

JamesS,

Yes - your explanation makes sense. I was just making the point that the engine revs don't necessarily need to be increasing at maximum torque given that the roadload could be such that the vehicle speed is constant.

In that situation, inertia effects would not come into play and the input torque would be whatever the motor was capable of producing. Surely the transmission would be designed about this worst case, or at the very least at the maximum kerb weight + maximum towed load etc.

Given that a turbo engine is never going to step instantly from minimum to maximum torque due to lag (even if it is less than 0.5 secs), wouldn't the dynamic load be not far in excess of the steady state load?

I see from your profile that this kind of thing is your area of expertise, so I'd be interested to hear a decent explanation.

As I mentioned, my car seems to generate full boost in all gears, so I don't think this behaviour is designed into the ECU.

Rgds,

Alex

 

Hi,
I have my my99booked in on the 30th. I am having the same problem, and post my results.

Cheers

Ian

 

Evozero,

Do you also have the 2500rpm to 3000rpm hesitancy (a bit like fuel starvation on my old MK11 Escort) as well as the lack of boost? Which dealer are you booked in with?

 

Hi all

I have an LED connected to the wastegate solenoid on my car(investigating overboost problem)
Normally it flashes at all revs and the length of the flash changes as the ECU changes the duty cycle of the solenoid to control the boost.

When my car does not deliver full boost in second (and sometimes third) the LED stops flashing and just stays on.This means the ECU is dumping as much boost as the control system allows,for what ever reason!

This just confirms what is already accepted ie the fault is caused by the ECU and not the boost control system etc.

Also if it is a torque limiting measure why doesn't it happen when the gearbox has to cope with the highest torque load of all which is during a racing start in first gear.

The engine is already spinning so the inertia of the flywheel etc has been overcome,in fact the kinetic energy stored in the flywheel etc allows you to apply more torque than the engine can produce.(for a short time)
In this situation the torque animals like Stef can apply to the transmission must be far higher than at any time in second gear.
James S do you agree with this or am I talking bo**ocks ?


[This message has been edited by AndyMc (edited 17-03-2000).]

 

AndyMc,

I can see where you are coming from, but the situations in the day to day life of a car where you give it maximum attack from a standing start in first (at Santa Pod, for instance) are likely to be far less frequent than standing on the throttle in 2nd from 3000 revs.

Remember also that Stef sha**ed his gearbox recently.

My 99MY uk car does this occasionally (although never gets the 2000 - 3000 hesitation under part throttle and pulls like a demon to the redline )and is a real pain. (And let some **** in a Vectra SRI the other day sit on my bumper out of a second gear roundabout - until I hit 5000rpm )

Doesn't only do it exiting corners/roundabouts though. I think it appears more prevelant in this situation because there is more likelyhood of holding revs in 2nd then flooring it when exiting corners, roundabouts etc than when on the straight.

What is interesting though is that everyone appears to have the same problem, ie hod revs, then get half boost (appx) from 3000 revs 'till about 5000 revs when all hell brakes loose again.

I doubt very much there are any sensors in the Scoob which can establish whether the car is cornering or not (although these are common in many applications), but it would be quite simple for the ecu to "know" what gear the car is in by the simple means of a sensor in the box or linkage for that matter, without going to the trouble of being aware of load (although that may be another possibility)on the transmission.

I suspect the programming would be quite simple for this feature.

Given the consistency of the problem car to car, I would doubt it is mechanical and more likely to be ecu related.

I assume it doesn't do it on cars with changed ecu's? If not then thats the problem.

As a thought, maybe it happens in first as well, but you can't tell because of the low gearing...

Just my thoughts

 

3000 miles down the line, it did it very slightly last Friday. And now the problem is back. I will be taking it back to the dealer again on Saturday. I would also say that my car was not doing it until about 11-13000 miles. Can we not all get together and complain more loudly. At least we all know the problem is not in our head.

 

Why not all chip in with a small amount of money to get one of the cars most prone to this problem inspected independently by experts. I have no idea who that may be but a few quid each could soon add up to employ a specialist. Once identified then IM could be tackled to sort the problem or at least we would know what the problem is.

I have had some hesitancy but sorted it by changing the brand of fuel that I use. I do not have the 2nd gear probs but would still be happy to chip in as you never know when it may strike.

Brendan

 

Mr Leigh,

Did you make any progress with fixing the 2500-3000 hesitation with the last visit to your dealer?

Julian.

 

My dealer had a look at this problem but couldn't fix it. After driving a brand new MY00 with exactly the same problem I am now convinced it is a design limitation. I have found that if I progressively push the accelerator down (rather than flooring it) I obtain full boost throughout the rev range.

 

Just read the thread.
My MY99 did this after its 1000mile service, so I took it back and found that the dealer had overfilled the engine with oil. They drained and refilled the oil and replaced the filter and it did seem to be ok for a while. Now done 15,000 miles and its been the same for ages. This drives me mad from 2500 - 3000 rpm floor it and it goes nowhere until 5000rpm. I'm going to ring Subaru UK and will post their response very shortly.
Regards
Martin

 

Spoke to Subaru and they reckon is emmision problems regarding the closed loop, whatever that is. Advised me to take it to my dealer.
Martin

 

Gentlemen,

Please allow me to introduce myself and tell you about my bout with "Hesitation," or '"H."'

I'm Gary Friesen from Marina Del Rey, CA. That is the boat marina you see to the north if you fly out west over the ocean from LAX.

I am an inventor and found the hesitation problem that lots of people were talking about to be of interest to me because I did not like driving cars that control me. I'm the driver here, the machine is not the driver!!

So I took it upon myself to solve my hesitation problem as soon as I had the second Subaru to do it to me. The first I thought was just an odd ball car. Then I realized that it was a Subaru problem, no matter what Subaru had to say about it.

I, of course, had a good group of interested drivers with the same problem.

I solved the problem, offered free advice on a temporary, do it yourself mechanical fix, and ultimately built a kit that fixes the problem electronically. I sell them.

**I will discuss the relationship to the turbo models after I tell you a bit more.**

I have had praise mail from all over the world come to me at my computer screen starting the very first day that I offered my first public explanation of hesitation, entitled " The Cure To Hesitation In Subaru Engines (c) By Gary Friesen hobiegary@earthlink.net(copyright) September 11, 1998 (all rights reserved) "

ONE OF THE FIRST REPORTS OF SUCCESS THAT I RECEIVED, CAME FROM A TURBO OWNER!

I was up against an American Company, Subaru of America (SOA), who was not about to admit to the problem. You see, in America when a company admits to a problem, they are liable to be sued for related catastrophes. For example, if anyone had ever died because their car "hesitated" in an intersection while trying to get out of a mad man's way .. and then if Subaru admitted that hesitation was an unsolved problem .. they might be held responsible for the death.

So when SOA denied it, I knew that going to them was the wrong approach. Further, Subaru of Canada HAD in fact admitted problems, or at least some of their dealers had admitted it.

** I will now explain what the was and how I approached the cure, but first I want to discuss hesitation in Turbo models briefly.

All I am going to say is that Turbo engine management is more complicated and regulated than non turbo and your hesitation may very well be the same problem as mine or not.

Having said that, I will tell you that I have had turbo owners tell me that my fix helped. I have sold to plenty of turbo owners. In all of my sales, turbo and not, I have had not one complaint. I'm happy about that.

Most of the classic described signs of hesitation in your cars match the signs of hesitation in American cars so I expect that many of you will benefit from my work.

I offered the first fix for free, still do. I offered the second for a price because it is better and I would like to be compensated for my time and efforts.

The first is still free for two reasons. One, as a Subaru enthusiast, I want to give to our community. Second, it is a great way for a person to find out if their car is going to be helped by my kit that I sell.

If the free fix works, then you will know that you need to buy the better one. If it does absolutely nothing, then you will know that you tried and further isolated your trouble. **

As an experienced back yard mechanic tuner, I identified by feel, a problem with my timing advance/retard regulation. This is much easier to isolate on a non turbo (my car is a non turbo, stick shift) car because variable amounts of boost make things even more changeable. Also, an automatic transmission will help mask problems as well.

I attacked the knock sensor circuit first since I felt that the knock sensor (KS) was the most probable item to cause a advance/retard management problem.

I was right on! After countless hours of experimentation I determined that the KS signal was not being discriminated adequately by the Electronic Engine Control Management Control Module Unit (ECU, ECM, EEC, whatever!).

My first success with hesitationless driving was without the sensor. This forced the ECU into not applying additional advance upon acceleration. Then I drove with a dummy KS to fool the ECU, no hesitation, but lots of pre-detonation (pings/knocks).

I decided to manipulate the sensor instead of the ECU since the ECU is a Erasable Programmable Memory that is extremely difficult to work with.

After KS signal manipulation by KS mechanical silencing/dampening (rubber washer under the KS) worked to cure the hesitation, I set out to tell the world and start to build my kit that would electronically dampen the signal once and for all.

I have fitted my kit to my car more than a year ago and have had perfect performance ever since.

My announcement on September 11, 1998 can be seen at:

 

Hey, mates!

I own a Forester Turbo with a Prodrive Upgarde (new ECU, dump valve and exhaust). The engine is almost identical to the Impreza WR. The problem is that the car from the day of purchase has the same problem. Starving for fuel and or air in low rpm (1500 - 2300) under 2nd gear. The service has tried everything but with no luck (under guarrantie) - they changed sparks, fuel regulator, MAF sensor but with no luck. I must also say that the Prodrive (STI) ECU is definetely facing the same problems with this issue as the ordinary ECU the car had. ( I upgrated after I had 16K miles on it). I installed a K&N filter keeping the air box and the problem got a bit smaller. My personnal belief is that the Knock Sensor is being sluggish under such rpms (1500 - 2500) and/or it hears other noises at that field that modifies the advancing of the engine. Please use the following address to visit Gary's Webpage who has a made a fix for the non-turbo engine facing the same problem.The address is: