Loss of peak power.....suggestions

[andycowuk 0]

EDIT - The title should perhaps be renamed "Shriveling torque curve" but to save any confusion I will just leave it.

 

Hi All,

 

This is going to be a bit of a monster post.......I can tell already!

 

I cant say I have a problem, because everything is working fine :lol: , but I will call it a situation...

 

I have had my car on the rollers 4 times this year, and not once the results have been the same. Even over the last 4 weeks, I have done afew things to the car, but still the peak torque has dropped by 300rpm..

 

I haven't scanned todays plot yet, but I will get it up tonight or tomorow.

 

 

This is the best by far. Not only are they the best figs, but more importantly the torque curve is nice and flat, and goes all the way up to about 5700rpm before it tails off.

 

The next time it was done was in april, and the numbers are pretty close to Jan's but the curve has kind of died off at the end, and the torque tails off after 5400prm.

 

 

I would be inclined to blame that on the boost which appeared to be down on Jan. So I checked for leaks, and replaced all of the rubber hoses from the manifold. I also replaced the fuel pump for a new one incase it was that.

 

 

I got the third one done last month and it is by far the worst. The peak torque fell to 4410rpm, and the area under the graph is much smaller that before. I changed the complete distributor, and leads expecting it to be hall sender related, and it does feel much better to drive.

 

The plot from today is a bit better with a better area underneath, but the peak torque is now at 4090rpm.

 

Anoyingly there is no boost plot on the last two prints, but the boost gauge currently indicates around 0.8 bar before bleeding just at the red line.

 

The things I can think that I have done to the car, that have a bearing on all this is:

Stg 4 G-Werks charger, RSR outlet - Std Corrado IC.

P&P Head/Charger/TB

Boost return Removed, carbon canister removed.

4 Branch Stainless steel exhaust header, Super sprint system.

in the last year - lamda probe, Plugs

in the last 6 months - fuel pump & filter, Knock sensor, Lamda Harness

in last month - complete distributo, HT Leads

 

SO, any ideas? And thanks for reading!!!

 

Cheers

[Supercharged 2]

I think it's fairly difficult to get a consistent figure out of a G60 because of heatsoak etc on the charger and the IC....

[andycowuk 0]

I think it's fairly difficult to get a consistent figure out of a G60 because of heatsoak etc on the charger and the IC....

 

The power and torque figures are not in question, the differences in the torque curve shapes are.

[stevemac 0]

When you had the distributor fitted - what was the timing set to ?

Have you changed types/brands of petrol ?

 

With those mods, you should be using Bosch W5DPO spark plugs - are you ?

(Standard fitment Bosch W6DPO will not be "cold" enough when you get higher in the rev range)

[W3RKD 0]

look at the air temps andrew they go from 12deg on the first plot up to 26deg on the last. these temps are going to have a key factor in bhp/torque Characteristics mate.

[andycowuk 0]

they guy had a digital thermometer sitting on the computer, it read 11 deg. The static air temp in my engine bay may have been 23, but surely the moving air being drawn into the charger is not that temp...it felt bloody cold on my ancles!

 

The only two things that went into my engine bay were the magnetic clip thing round the ht lead for RPM, and a boost tube onto the small hose from manifold to FPR. the 23 degrees, were definately not in my engine bay!

[Joe M 0]

More bad news then, if the temp was set too high then the rollers will be overreading.

[andycowuk 0]

More bad news then, if the temp was set too high then the rollers will be overreading.

 

Do you mean that the rollers adjust the figures reletive to the ambient temp? Surely they would scale it on a linear basis, and therefore would just move the cuve up and down the power/torque axes, and not alter the curve shape.

 

Darren, taking into account the ambient temps, (and assuming they are correct) would you say that I am chasing a problem that dosent exist? I want to make sure everything is sweet before I do some more mods, if it is heat soak, then the fmic will solve it, but what I dont want to do is mask a problem with a mod.

 

Oh, and my bloody door handle broke today as well. :roll:

[Joe M 0]

The first graph shows 175.5@12degrees C

Last one shows 161@26degrees C

 

Now its been pretty cold today, probably less than 12 degrees, if the rollers had been set too 12 or less then there wouldnt be as high a correction factor added as there was, giving a lower figure.

 

Basically what im trying to say is the temps today were probably similar or less than when you had the first run done and you had 175.5, today it was probably a bit less than 160, so it doesnt sound to me like its a temperature issue causing the lower readings.

[andycowuk 0]

stevemac, the timing was not set to an absolute value. I just drove it, watched the boost gauge and listed for pinking. I set it as far advanced as I could then backed it off a bit, and reduced the co pot from 550 to 480.

 

While the w5dpo plugs may well be better for the job, the first plot was on w6dpo, so i would expect to be able to come close to a repeat of this run without changing the plugs. The first plot is on optimax, and I am certain the second one is too. The third is on BP ulitmate, and todays which, as I say is slightly better, was on ESSO Super 98 ron, that I came across at a filling station in Thurso last weekend, so if anything should be better.

[Henny 0]

how old are you injectors Andy?

[andycowuk 0]

Me and Joe were discussing this on MSN last night. Injectors are original, I have recently run a load of injector cleaner through the last couple fo tanks, but they havent been tested for flow or spray pattern in last year. How can I get them tested without being car-less for a couple of days - can i take the rail and injectors out, and apply 12v to injector harness and spray petrol into a basin onto of the engine? - how does the rail attatch to the fpr again, i forgot!?!?!?

[stevemac 0]

andycowuk, If you have a local Bosch service agent - they should be able to test the injectors while you wait. They'll need removing from the car though.

[h100vw 0]

andycowuk, If you have a local Bosch service agent - they should be able to test the injectors while you wait. They'll need removing from the car though.

 

Andycowuk, this sounds like a garage clearing opportunity :lol:

 

I have the original injectors from my Golf. They were removed to fit the reds. They are sat in the top of my tool box in a bag. For a small fee, negotiable, you could have them checked out and replace yours with a known good set? If the turn out to be no good I'd do you a refund on their return.

 

Gavin

[andycowuk 0]

Gav, that sounds like a plan. Will get all eight cleaned and tested, then use the best four - I wont need to return them to you if they are not the problem - quite happy to spend the money and know that things are in good shape.

 

Luckily I have a bosch service centre about 200 yards along the road......just next door to the VW dealer! 8)

[andycowuk 0]

I have been quoted around £20 per injector to get them cleaned and tested.....a bit more than I had thought!

 

I have never had this done before, so dont know if this is a good or bad price - anyone care to comment?

 

Thanks

[dr_mat 0]

Bargain. £80 for four? You can do mine then! I'll send you six of the blighters..

[h100vw 0]

Red tops are 110 quid, doing myself out of a sale but why use old gear? A new chip isn't that much to go with the injectors.

 

Gavin

[andycowuk 0]

You are right about the price gav, but the chip isnt very much, and then there is the pully that isnt very much on top of that, and then I have the standard intercooler........

 

It may sound silly or even slightly anal, but I am happy to spend £80 to make sure everything is in tip top shape, and then go on to do the modifiactions. At £80 for 4, I will get mine cleaned, and if any are beyond repair, I will take yours off your hands.

 

dr_mat, wouldn't be a problem.

[jezzaG60 0]

Looks like you have some VERY dodgy dyno plots there mate, i'm guessing there is probably nothing wrong with your car.

 

1. Always look at the figures quoted "at the wheels". These are what the dyno actually measures. Flywheel figues are usually a bit of a dodgy guess.... as a rule tho Bosch say transmission losses for a FWD car will be about 15%

 

2. Torque and BHP curves should cross eachother at 5250 rpm.... its a fact.

 

The crossover point of 5250rpm tells us:

horsepower = ft.lbs * rpm / 5250.

(When rpm = 5250: "rpm / 5250" equals 1, so it reduces to "hp = ft-lbs")

 

If they don't you need to start questioning why!

 

Looking at your wheel figures there is actually very little difference... about 130hp at the wheels.... that said though for the mods you have their doesn't seem to be the power you would expect.......

[Joe M 0]

2. Torque and BHP curves should cross eachother at 5250 rpm.... its a fact.

 

The crossover point of 5250rpm tells us:

horsepower = ft.lbs * rpm / 5250.

(When rpm = 5250: "rpm / 5250" equals 1, so it reduces to "hp = ft-lbs")

 

If they don't you need to start questioning why!

 

 

The graphs above where it doesnt cross over at 5250 are easily axplained by the fact the torque and power curves are being measured on a different scale.

[andycowuk 0]

Here is a copy of my last power run - two runs done back to back..... the peak power is 152bhp.... which is way down.

 

 

That is after having the cleaned injectors put back in.....

 

Next step is to get a garage to do some proper diag on fuel pressure/boost/knock sensor/timing..

 

unless there are any other ideas?

[Supercharged 2]

Not being funny Andy but are you sure the throttle is opening fully?

[andycowuk 0]

yes, i have played about with the wot switch, and had the complete tb stripped as it was a bit sticky...i know for a fact return b/f is 100% closed, and that throttle b/f is 100% open

[jezzaG60 0]

OH yeah, sorry, didn't notice the scaling differences.... that will teach me to post replies at midnight! Al my dyno plots are on the same scale which makes things easier to compare. I still think its slightly odd that there is such a big difference in "flywheel" hp and only a small measured wheel difference. That said... correction factors for the dyno include many things.... ambient temperature, hunidity and air pressure. These are combined to give the "corrected" bhp.

One other thing to note.... we always keep a note of the tyre pressures.... it helps to produce dyno plots which can be compared... i'm always surprised by the difference 5psi in the tyres can make.

 

Anyway, thats enough of my rant about dyno plots.... it does seem that your car is progressively loosing a bit of power so there probably is a problem somewhere. Do they have a gas analyser or Wideband O2 hooked up during the runs.... would be nice to know what the fueling is doing.