Better performance on B20 - so what's wrong??

JLKunka

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'99.5 Jetta - parts car, '99.5 Jetta - black, '02 Jetta - silver, '13 Jetta DSG - black
'99.5 Jetta - 180,000mi

Let me explain: Ran a tank of B50, clogged the filter pretty quickly. Put new filter in, car ran great. As I drove and refilled with straight pump diesel, performance began to fall off. The engine would struggle to reach 4000 RPM. I figured it was the filter clogging again, but I put a tank of B20 in and performance came back instantly. The engine is rev-happy again.

I ask what is wrong because with the added viscosity of the biodiesel, something is causing the engine to deliver more fuel. It must be one or more of the following:
  • worn injector bodies/plungers
  • worn injector pump
  • bad pump seals
So in your opinion, what is the most likely cause? I'm planning a nozzle upgrade soon, so I don't want completely new injectors if I don't need them.
 

bluesmoker

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biodiesel has less engergy (btu) than straight d2, if you use higher blends of biodiesel you will notice a loss of power

its normal
 

J double R

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bluesmoker said:
biodiesel has less engergy (btu) than straight d2, if you use higher blends of biodiesel you will notice a loss of power

its normal
exactly.. so why is he noticing LESS power with D2, and MORE power with bio? (i'm certainly at a loss)
 

JLKunka

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'99.5 Jetta - parts car, '99.5 Jetta - black, '02 Jetta - silver, '13 Jetta DSG - black
"biodiesel has less engergy (btu) than straight d2, if you use higher blends of biodiesel you will notice a loss of power"

Yes - I realize that. Read the post again please - the opposite is happening. I'm getting better (let's say normal) performance on B20. Reduced performance on straight diesel.
 

bluesmoker

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JLKunka said:
"biodiesel has less engergy (btu) than straight d2, if you use higher blends of biodiesel you will notice a loss of power"

Yes - I realize that. Read the post again please - the opposite is happening. I'm getting better (let's say normal) performance on B20. Reduced performance on straight diesel.
oops,sorry first thing in the morning.....lol, i need a coffee:eek:

the only explanation i can have is the b20 has a higher centane (straight bio is about 60-65) d2 is around 45

perhaps this is the explanation
 

JLKunka

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'99.5 Jetta - parts car, '99.5 Jetta - black, '02 Jetta - silver, '13 Jetta DSG - black
"the only explanation i can have is the b20 has a higher centane (straight bio is about 60-65) d2 is around 45"

I know my static timing is a little late - cold start valve is at 60% duty - but the ECU can still meet target timing. So you think the extra power could come from the more advanced burn of the B20?

Any thoughts on the higher viscosity?
 

grizzlydiesel

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im in the higher cetane boat. my truck ran better with B20 in the tank. quieter, smoother, less smoke. but it was hard to tell if there was a performance differenence, the truck isnt exactly an autocrosser ;) ill be filling up with B20 in the tdi at the next fill up, but havent yet so i cant say if it effects performance in one way or the other.
 

Keith_J

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Check fuel flow rate. At idle, you should be pumping about a pint per minute. If not, check the fuel lines from the tank to the injection pump
 

JLKunka

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Check fuel flow rate. At idle, you should be pumping about a pint per minute. If not, check the fuel lines from the tank to the injection pump
__________________
2k Jetta manual. PP520s.
To check: Do I disconnect fuel return hose at filter, collect in a jar and time for one minute?

im in the higher cetane boat. my truck ran better with B20 in the tank.
This is a significant difference. Engine won't rev easily to 4000 on regular diesel. No one thinking of extra fuel viscosity helping anything?
 

Keith_J

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JLKunka said:
To check: Do I disconnect fuel return hose at filter, collect in a jar and time for one minute?



This is a significant difference. Engine won't rev easily to 4000 on regular diesel. No one thinking of extra fuel viscosity helping anything?
Yes. Make sure the engine is warm to the thermostatic tee is bypassing the filter.

My hypothesis is the BD caused junk to partially obstruct the fuel pickup in the tank. You had an issue with the filter so the check valve in the sender might be obstructed. It is easy, if not messy, to clean.
 

4Gman

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J double R said:
exactly.. so why is he noticing LESS power with D2, and MORE power with bio? (i'm certainly at a loss)
Biodiesel adds lubrication. I have read that blends up to 20% can actually increase fuel economy for this reason. And maybe it's much needed with the recent switch to ULSD.
 

J double R

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4Gman said:
Biodiesel adds lubrication. I have read that blends up to 20% can actually increase fuel economy for this reason. And maybe it's much needed with the recent switch to ULSD.
economy, sure. but we're talking power, which has always been known to take a slight dip with bio use. ;)
 

grizzlydiesel

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Tbirdtree said:
Mabey you just got some bad D2?
thought about saying that, but i guess i assumed there had been more than one instance of the power drop. and it just seemed to simple to be the answer ;)
 

flycut

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michigan
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this was discused on a diesel truck site by moparman1973 b20 was said to give more perf due to thicker vescosity compensating for worn pumps . also if you search moparman1973 he has a site with some very good tech info on fuel and additives lubricty and btu it burns at
 

JLKunka

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Originally Posted by Tbirdtree
Mabey you just got some bad D2?
Let's back up a bit. The last tank of "B20" was a little misleading. I'm running on straight petro diesel, and notice the loss of power. When I've used 3 gallons of the full tank, I add straight B100, so I end up with B20-ish. The same presumably "bad" petro diesel is still in the tank, topped off with B100. As soon as the fuels mix, the power is back.

I'm going to push once more and ask to consider what the increased viscosity of the fuel would do to make more power. More fuel is now reaching the cylinders to make more power, but where is the fuel going when the tank has plain petro-diesel?
 

jcrews

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JLKunka said:
"the only explanation i can have is the b20 has a higher centane (straight bio is about 60-65) d2 is around 45"

I know my static timing is a little late - cold start valve is at 60% duty - but the ECU can still meet target timing. So you think the extra power could come from the more advanced burn of the B20?

Any thoughts on the higher viscosity?
But can it do so at 3800 RPM?

Symptoms of basic timing too retarded:
Black smoke
Poor performance

I agree with your second thought on the bio blend having a short enough ignition delay to mitigate the effects of retarded injection timing.

Reset your basic settings and see what happens.
 

JLKunka

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But can it do so at 3800 RPM?

Symptoms of basic timing too retarded:
Black smoke
Poor performance
I'll log a run to verify...but once again, engine labors to reach 4000 rpm on petro diesel, but revs easily past 4500 on B20. Just way more power throughout the rpm range on B20, especially above 3000.
No smoke in either case.
 

Tbirdtree

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JLKunka said:
Let's back up a bit. The last tank of "B20" was a little misleading. I'm running on straight petro diesel, and notice the loss of power. When I've used 3 gallons of the full tank, I add straight B100, so I end up with B20-ish. The same presumably "bad" petro diesel is still in the tank, topped off with B100. As soon as the fuels mix, the power is back.

I'm going to push once more and ask to consider what the increased viscosity of the fuel would do to make more power. More fuel is now reaching the cylinders to make more power, but where is the fuel going when the tank has plain petro-diesel?
Just an idea. On a similar note. When I was on a trip a while back, I filled up with some bad B100 about 10 miles into it I had real bad acceleration, especially up hills. I drove it down a quarter tank, topped up with some D2 and about 10 miles later, car was driving just fine again. Opposite senario, but it is possible. I agree that running B10-20 my car feels real good. At B100 there is a noticable power drop, not huge, but noticable. I usually try to stay at about B50 now a days.
 

JLKunka

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flycut said:
this was discused on a diesel truck site by moparman1973 b20 was said to give more perf due to thicker vescosity compensating for worn pumps . also if you search moparman1973 he has a site with some very good tech info on fuel and additives lubricty and btu it burns at
Thanks, I'll look for this. I heard the same about injectors. The clearances are tiny, but at such pressures any wear means more leakage past the plunger. Higher viscosity means less leakage.

Think of the classic compression test for worn rings. Air (low viscosity) blows by worn rings easily. If a teaspoon of oil (high viscosity) brings the numbers up, rings are bad.

Still I hope to hear from someone that my pump and injectors are probably OK, it's just seals. (Though I don't see what seal can cause this problem).
 
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