TDI FLAT SPOT ??

[KINGPRAWN]

Had my 1z TDI conversation done a few years ago and it's been absolutely trouble free ( the odd water hose fail but nothing more) ... I performs perfectly except for a flat spot/limiter feeling I get when climbing a hill , all power builds nicely and it pulls strong until I hit 2600 rpm when the power just stops building and we hit a plateau and the building stops with a noticeable hesitation!!! Any ideas ???? Only noticeable when climbing..... Thanks in advance

[davegsm82]

To be fair this could be normal, my AFN doesn't develop much over 3-3500 ripems, everything is much lower down in the Rev range. Are you using an intercooler? have you had vag-com plugged in to make sure all the sensors are operating sensibly? (MAF, MAP, IAT, CTS blah blah...)

When you're climbing you're under max load so that's obviously where anything marginal starts to present itself. I was getting a little bit of fuel starvation which was caused by air in the fuel feed to the pump, I hadn't really paid attention but even at idle there were streams of BIG bubbles going along the fuel pipe. Turned out to be the fuel filter letting in air, a replacement filter solved the air ingestion and thusly the starvation. Any air in the fuel intake is bad news, the pump uses fuel as lubrication.

[KINGPRAWN]

Thanks for the reply .... It's something that I have noticed for a good couple of years , it makes no real difference to how it runs but it's just a little annoying, I can come off a roundabout near to where we live in second, hit third quite quickly pulling and building nicely then feel a definite restriction !!! Then all building power stops and I just carry on but at that constant .. No more building ????? Have A SCANGAUGE so I can see intake temps are fine ... But have no access to vag com

[davegsm82]

You should get hold of a cheap clone Vag-com cable (fiver from ebay) and a Demo (free, usually supplied with the cable) copy of vagcom. This will give you the functionality you need to do the tests I believe, from what I remember you can't do logging but you should be able to see the demand and supply of boost, air flow and temperatures etc. there are 'illegal' copies out there but I don't know anything about that.

Have you (had it) checked to make sure your turbo is set up correctly? the actuator/wastegate (delete as appropriate) arm has to be set up right else it can cause all sorts of odd problems.

Mine's feeling a bit flat at the minute but that might be because my daily driver is a 150BHP PD engine'd MK4 golf.

Dave.

[KINGPRAWN]

Thanks Dave ... Guess vag com here I come !!! I know nothing about how to set the turbo ??? Where is that info to be found ???

[davegsm82]

Thanks Dave ... Guess vag com here I come !!! I know nothing about how to set the turbo ??? Where is that info to be found ???

There is info floating about the internet, but basically what I've done on VNT turbos in the past is;

1 - start the engine and make sure the actuator pulls in fully (hits the adjustable end-stop, don't adjust this!).
2 - run vagcom, monitor MAP requested vs MAP actual
3 - go for a drive and ensure the two follow each other approximately during various driving areas, on the flat, accelerating, uphill etc etc (this is where the graph function of a full copy of vagcom comes in handy).
4 - If underboosting (actual < requested) then shorten actuator by 1 turn. If overboosting, do the exact opposite of underboost.
If the MAP's are approximately equal then your boost system is working fine. If the actuator doesn't pull in fully, then either the turbo is jammed, actuator is holed, vacuum system has a hole in it (pipework), vacuum pump is failing or the N75 valve is roached.

I'm led to believe that the setup for wastegate turbo's is essentially the same but I've not had any experience of setting one up.

Any questions just give me a shout.

[KINGPRAWN]

Vnt is newer kit than mine ....

[busbuddy]

2600 rpm is a very odd figure to hesitate at

what gearbox you got
are you certain its 2600 rpm
what revs do you reach on the flat

max torque on the 1z is at about 2000 rpm but they will rev freely to 4000 rpm but your symptoms sound like you have run out of revs, reached top speed, are you getting full throttle

the pump will rev until it reaches its limit then it freewheels (so to speak) and the fuel is cut down to keep the revs down, it feels like a speed limiter in a truck, which is like the symptoms you describe

[KINGPRAWN]

That's exactly as you describe.... Standard 2.1 syncro box standard engine from 96 mk3 golf less the air filter..
Could I just need different injectors then ??? Thanks

[KINGPRAWN]

Sorry half reply .... On the flat/ down hill frees across the dial .... Have a tacho and a SCANGAUGE so deff 2600 ... But only when pulling up hill !!!

[randolph57]

Hi

As Busbuddy inferred are you sure that your throttle potentiometer is fully open-If you are using a donor 'barrel' type via the old throttle cable or 'under the pedal' modification it may not be sending 100% throttle open signal when your pedal is on the floor.
I am working abroad at the moment so from memory I can configure my ultra-gauge to read throttle position from 0-100 or the other way round(as per preference) so I imagine this can also be read on your scan-gauge. This normally just requires the ignition on and power to your gauge so may be a nice easy check to do.

[davegsm82]

When you say 'less the air filter' do you mean you don't have one installed?

I only ask as I had a Cone filter (K&N style) and it was horrible, noisy and created a flat spot in the middle of the rev-range. reinstating the original JX air filter can works wonders.

Dave.

[KINGPRAWN]

That is exactly the filter I have .... was very pleased with it , hadn't noticed the noise ???