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Engine Specific Info and Questions => IDI Engine => Topic started by: arsenicpants on April 20, 2011, 09:56:14 pm
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My car tops out at 110/120 km/h, and it always has
from when it was an NA diesel with a 7A, to a 1.6TD with a 7A, to now with a 1.6TD and an FN
from stock size wheels, to 15" wheels with 50 series tires, to now 13's again with 50 series tires
every time i do these upgrades i hope to God it will go faster than 110 km/h but it never does, and it's driving me absolutely crazy
so what the heck is wrong? what can i do to increase the top speed? i don't mean like "YEAH, I WANT TO GO FASTER!" i mean "Yeah, i'd like to be able to keep pace with traffic and not feel like the engine is about to explode"
can anyone help me out?
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How much boost are you running? Does it smoke when you're trying to go faster? How high is it revving?
I've had my NA rabbit with a FN tranny up to 80-85mph with the revs around 3500rpm.
Is your governor kicking in?
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Either you're driving a 1.6TD school bus or you've got issues.
that's exactly what i mean; what could the issues be?
How much boost are you running? Does it smoke when you're trying to go faster? How high is it revving?
Is your governor kicking in?
it's running about 15lbs of boost with a k14. it doesn't smoke, no grey, no white, no black, nothing. it's revving really damn high at the top of 5th, although i don't know exactly since it's a mk1 and finding or making a tach for it isn't exactly easy
it has not been de-governored as far as i know, or can tell, although having never driven a car that i 'know' has been de-governed i'm not sure. the previous built the motor and i'm waiting on conformation from him
can extra power increase maximum speed?
i was under the impression that more power just got you to that speed faster?
the motor has relatively low mileage (rebuilt less than 50,000 km ago) and runs strong
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can extra power increase maximum speed?
The simple answer is: yes.
The simple explanation is that a vehicle's speed is the balancing point between the energy the engine puts out vs. the energy the vehicle consumes. The vehicle "consumes" energy thru forces like friction but most notably (in terms of max speed) wind resistance... a resistance that increases with speed.
More engine power -> more energy to push thru wind resistance -> higher top speed.
You can also see that decreasing friction is another way to gain top speed... dragging brakes?? Tight wheel bearing(s)? Poor wheel alignment? Beat tires / low tire pressure ?
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There is a point where extra power will not overcome the aerodynamics of a given vehicle but you are nowhere near that point and I don't think a 1.6td could ever be tuned to get you there in a mkI.
Use this to calculate rpm for a given speed: http://www.scirocco.org/gears/
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thanks
so i guess i've got a lot of tuning to do, and doing the governor mod if it hasn't been done
i'm almost positive it hasn't, it really doesn't feel like it from what i've read about it
I've used the gears table a bunch of times to help me calculate, but it seems pretty inaccurate
i mean, if more power can increase top speed, then wouldn't the RPM at any given speed change depending on the amount of power you're making?
according to the table, if i'm at 4500 RPM at 110 km/h now, i'd have to be running 7 or 8000 RPM before i'd get to anything close to normal
also, has anyone noticed that if you you put 'Kph' instead of 'kph' (first letter capitalized) you get a completely different RPM reading?
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Unless you have a van pump, you should be able to rev to 5200.
I had an NA Fox up to 100 MPH, but it took awhile to get there.
Turbo it sholdn't be a problem, gear limited speed in my caddy+T was 126 (200 KMH)
I never got it going that fast, but criusing at 75-80MPH was no issue.
is your fuel filter 10 years old?
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you have to know your rpm.
if you are toping out your rpm the only soluction is a longer geared gearbox.
no matter how much power you have if you dont do more rpm or change gearbox ratios, you will never have more spped.
110 is really low!
try to get a 4s or 4t gearbox, they will do around 180/200km/h.
i had that problem on my passat,it would top at 180.changed to a tdi gerabox and no more high rpm/low speed problems.
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If the gov mod hasn't been done then you are not reving too much. It will stop you when it hits it. Since you don't have a tach and don't know what it is reving then I would say you probably aren't reving as much as you think. It is basically more like a gas car in terms of revs. It sounds pretty bad unless you have seen one rev too much then you realize what these can handle.
I would ask what the PO timed the engine to and check out how to make your 1.6td a faster car. The main fuel screw is your friend.
The FN gearbox is pretty tall. .71 5th and the 3.89 final...the only way to get more top end would be with a 3.67 final. It isn't your gearbox.
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I have a 325,000km n/a bolted to a FN in my 84. I did 155km/h on the .... er.... closed course of course ;)
pic for proof,
(http://i299.photobucket.com/albums/mm307/J_holubek/84%20Jetta/IMG00594-20110408-1630.jpg)
With my FN and tires 185/60/14's, I was spinning about 3950. Also I have done 130 in 4th, which i spin 4300.. OR 115 in 3rd! 5250!
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has anyone noticed that if you you put 'Kph' instead of 'kph' (first letter capitalized) you get a completely different RPM reading?
I just messed with that and if you put anything but kph the calculator defaults to mph.
What size tires do you have? I used 175/70R13 and a FN tranny (my setup) in the calculator and @ 4500rpm = 176kph. It appears as if your max rpm in 5th is 2802rpm.
if more power can increase top speed, then wouldn't the RPM at any given speed change depending on the amount of power you're making?
according to the table, if i'm at 4500 RPM at 110 km/h now, i'd have to be running 7 or 8000 RPM before i'd get to anything close to normal
Doubling the rpm in a given gear WILL double your speed, 8K rpm will get you up to 314kph or 195mph.
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What is your exact tire size?? Roughly figuring, with at 7A at 110kph (68 mph) you should only be turning the engine a tad under 2800 rpm.. Even without a governor mod you got more to go...
You say it was NA and now is TD, is this with the same pump??? I'm not saying you can;t use a NA pump, on a TD, but if it's the same pump, maybe there is a pump issue.. Or else you got some other variety of fuel starvation issue such as an air leak, plugged screen in the tank, 10 year old fuel filter.. If brakes were dragging that bad you'd have smelled that by now.. What's the timing set at?? How's the clutch???
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i've had my old stock 1.6td jetta at 190km/h once. Down hill...A really long hill. Rev's were maxed out with a 4S tranny.
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What is your exact tire size?? Roughly figuring, with at 7A at 110kph (68 mph) you should only be turning the engine a tad under 2800 rpm.. Even without a governor mod you got more to go...
You say it was NA and now is TD, is this with the same pump??? I'm not saying you can;t use a NA pump, on a TD, but if it's the same pump, maybe there is a pump issue.. Or else you got some other variety of fuel starvation issue such as an air leak, plugged screen in the tank, 10 year old fuel filter.. If brakes were dragging that bad you'd have smelled that by now.. What's the timing set at?? How's the clutch???
The motor and pump came as one, and it's a proper TD pump, it doesn't leak or anything
I replaced the filter when I did the swap
Actually, I updated it to the mk2 style filter at the same time
Looking at the fuel lines when it's running I can't see any air bubbles, well maybe 1 or 2 small ones, but nothing huge
No idea what the timing is set at, I'll have to figure out how to tell
It could very well be something in the tank, is there a way I can test to see or run something through to possibly break it up? I'm guessing I'll have to crack open the tank and have a look
Thanks for the suggestions, I'll make a list and see if I can track down the issue, or issues
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From a safety standpoint this isn't a good idea for driving down the road at 120 kph, but If you could run it off a container of fuel instead of the tank that would work to rule it out.. Does the engine seem to rev up to a certain point then poop out at the speeds mentioned, or can you push it any further(even though it sounds like it's screaming already at that point)
Since it has been 2 different pumps, I kinda *suspect* that isn't your problem. 2 difference engines can sort of rule out timing too, but it can't hurt to check.. Timing retarded would make it start like crap too..
Are you absolutely sure you have a 7a trans?? Another thought, although incredibly rare and odd, how's the exhaust look? Does the muffler have anything rattling around inside?
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get a tach
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From a safety standpoint this isn't a good idea for driving down the road at 120 kph, but If you could run it off a container of fuel instead of the tank that would work to rule it out.. Does the engine seem to rev up to a certain point then poop out at the speeds mentioned, or can you push it any further(even though it sounds like it's screaming already at that point)
I might try that, just hooking up an auxiliary can to it and see how it runs, that's a good idea
It does seem to just hit a wall at 120, and I can accelerate from 90 to 120 very quickly, but as soon as I get there it's like "aaaaaghhh!! Ok that's enough no more!!" I 'can' push it to a higher rom and maybe to 130, but it gets there very very slowly and at that point it just sounds and feels like the engine is really working waaaaay too hard and it's going to poop a brick or something
Since it has been 2 different pumps, I kinda *suspect* that isn't your problem. 2 difference engines can sort of rule out timing too, but it can't hurt to check.. Timing retarded would make it start like crap too..
It starts instantly every time, and only shudders a little after starting if it's been sitting outside in te cold for a long time
Are you absolutely sure you have a 7a trans?? Another thought, although incredibly rare and odd, how's the exhaust look? Does the muffler have anything rattling around inside?
The old transmission was a 7A, that's what the case said
I was almost positive that the 5th gear had been swapped out for something much worse at some point in it's life, but this new FN is exactly the same thing, Only a slight bit better, so I've kind of ruled that out
The exhaust is brand new 2.5" straight back with no muffler and a TT downpipe
get a tach
I've got a CE1 diesel cluster with a tach sitting on my shelf, but I think it's worth more to someone in the states than to me, so I haven't cracked it open yet
I may get brave, or stupid, one of these days
I'm away from home now but will try the suggestions when I get back monday
Thanks
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Check your IP timing & make sure the cam hasn't slipped back / retarded a bit, due to cranking on the tensioner pulley or something during the final tightening process. That could definitely have a negative effect on higher-RPM power output.
Rumor has it that the wider tires also really add a lot of friction.
[With 195/60-14, my 1.6n.a. Dasher wagon (2400lbs) hits 4000rpm (110MPH) in 5th gear (0.60 ratio), and it's still pulling very strongly, with quite a bit of travel left on the go-pedal. Unfortunately that's just running with the maniacs in morning commuter traffic, not on a closed course, so IDK what the actual top speed really is. I normally cruise @ 65MPH in 4th gear (0.77 ratio) for better fuel efficiency, safety, and less chance of police intervention, jail time, etc.]
J.R.
SoCal
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I can easily surpass the 110 KM mark, I'd say timing was the issue. When I first purchased my jetta it was really sluggish, turned out timing and a pinched tail pipe were the culprits.
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Are you getting full throttle on the pump when your foot is to the floor?
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I had this same problem, but mine kept getting worse, I went from good, to wheres my power, to... i can only go 65mph????
My problem was the throttle cable, it somehow managed to loose a clip or re adjust its self. (on the injection pump) I was only getting maybe 3/4 pedal, This afternoon it went to maybe 1/4 pedal, and by then (only able to go 55mph) I had had enough, thats when i could see the throttle cable pull out of its place with the hood up. I bought a crimp and crimped one side down, and re clipped the threaded side
Try adjusting it and see if that helps, only takes half a minute to do, and it might give you that extra inch of adjustment that you need to increase the fueling on your IP.
It made mine blow smoke and peg the boost guage at 20psi, I had to turn my smoke screw back to stock, and it still hits 15+psi on a hard pull.
Hope this helps
-Ron
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185/60/14
AVX
Pump good timing set less than 3000 miles ago with new belt
Throttle cable good, pulls good for the Eco (from what I gather)
Tire pressures checked, rolls well (40 psi all around)
I do not like to drive over 65 as it is rolling at 4900/5000rpm at that point.(I cringe at the thought of all the times I ran it at 70mph on the interstate before I got the tach) I have been reading about the different types of transmissions and have located a turbo diesel way down here in FLA sitting in a quiet corner of a junkyard. I am actually going to check the trans code tomorrow. (Crossing fingers for ASF)
Using the Scirocco rpm calculator, I ran the numbers and they are not matching what I am running. Plugging in my tire size and the 4.25/.75 final and fifth, the calculator says I should be running at 3062 rpm and I am almost 2000 rpm above that. Than I played around with the final and fifths that were on the similar trans codes and when I matched 4.25 to the 1.26 of the 16v motorsport I came within a hundred revs of what I am actually doing.
Could something else in the drivetrain, say maybe a worn clutch or smaller diameter flywheel, cause my numbers to be so off? Or did I happen to get the uber 16v motorsport tranny by sheer luck? ::)
(Also hoping this helps OP in some way)
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2000 extra RPM sounds well beyond the range of normal differences in tires etc..where did your tach come from... and how was it calibrated? :)
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VDO Vision from summit on the W terminal. Timing light. (Its awesome having a friend who drives a SnapOn truck) and your post on a thread about the switches which was spot on btw.
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Hmmmmm...there goes that theory. ;) ;D
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I was hoping Obi VWan would theorize a little more than just the tach! ;D
You thought I got a Sunpro and winged it didnt ya? :D
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Do you have any other trans to try? Flywheel would make no difference. A slipping clutch would, but it wouldn't be consistant. The AVX is probably the worst trans to have and maybe someone messed with the gears in it.
Does it pick up amazingly fast? If you are running that low of gear I would get another trans and keep that as spare.
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Do you have any other trans to try? Flywheel would make no difference. A slipping clutch would, but it wouldn't be consistant. The AVX is probably the worst trans to have and maybe someone messed with the gears in it.
Does it pick up amazingly fast? If you are running that low of gear I would get another trans and keep that as spare.
OH YEA! that thing should take off like an 8th mile drag car with an AVX in it..
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I dunno about a drag car but it revs up fast, I am shifting outta first before the speedo reads 10 mph. 3rd comes at 30, 4th at 40 and I can run fourth up to 50/55, and than top out at 70 max rev. But I hold off at 60-ish.
I found an ACH and an ACN at the junkyard I hit today. Now I just need some time off to pull it. Looking at the Gear Up site I think I am gonna snag the ACN.
This junkyard is awesome. Hundreds of air cooled of all types, Ghias, 412, Sambas, couple of "Things". Also has a good amount of water cooled Mk1-3. Jettas, rabbits, golfs, quantums, vanagons a few passats. I took a bunch of pictures. Ill be posting it up soon. It has a Diesel Jetta Coupe sittin there motor and all!
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i built and tried out a little fuel tank for the jetta today to bypass the regular tank & hard lines
at first it seemed that it made all the difference; in the first block of driving i could take it farther in all gears (60k in 2nd!) but as i drove it it seemed to go right back to the way it was before. i took it out onto the freeway after a few minutes of street driving and it still stopped short at 120km/h, pushing it
but really, i did notice a difference at first
also, the engine seemed quieter, and the turbo didn't seem to be working as hard all the time
I had just the fuel inlet to the pump hooked up to the extra tank, not the return (the return still went to the stock tank), and i had the extra tank venting from the top
could this be why? somehow? is the tank pressurized by the return?
i looked under the car at the lines and it looks like one of them is smushed a little. i remember driving over a giant rock ages ago, that must have been when it happened
the tank looks fine, clean and dry, although i realise the inside could still be gross. I'll have to pull off the cover and have a look inside
i've decided i'm going to buy new hard lines and redo them, even if that's not the problem. it's cheap enough to do
i haven't tested the timing yet, although it starts up easily even when it's a little cold, could it be too far advanced?
thanks for the help
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Sounds like you are on the right path. Change points often start with incidents, whether an accident, maintenance or whatnot.
I had a clogged fuel line that had the same symptoms a few years ago, now I have a clogged vent tube and does the same when the tank is less than half full.
Keep us posted on the results, for the next guy who has the same problem.