stuartg40

Hello all, this is my first post and I'm hoping someone might be able to shed some light on a slight problem with my 2003 Octavia VRS (30k miles).

I recently had several remaps done by a guy on eBay until eventually we got one that was consistently quick (other maps were fast sometimes and slow others!!). However, I did notice that if you opened the throttle up partially, usually between 2 and 3000 revs and then kinda eased off the gas, the car would jolt a bit; like a very sudden and brief deceleration (as if turbine had spun down very quickly maybe?!?!). If you booted it and then came off the gas you just got a nice dump valve noise and it was smooth coming off the boost.

So, I assumed it was a fault with the remap, especially seeing how I'd had 4 maps up to this point to try and get a fully working/compatible one. I went to a local Revo dealer who uploaded the 5-hour trial for me, but the same thing happened, only a little less noticeable, (the Revo map wasn't as quick as the one I'd had on before).

Now that the trial has run out and I'm back to stock speeds the problem has gone entirely. Can anyone tell me what would cause this effect? Is it normal after remaps? If it's due to higher boost levels why does it not do it at full boost/throttle? I want more performance from the car but didn't expect to have that niggley irritating effect as a consequence.

Thanks for reading and I look forward to your replies.

Stuart.

Lummox

Sounds like a possible boost leak to be and when its running a higher boost level its maybe letting a bit go.

A good health check is required I would say paying attention to the pipes under the inlet manifold.

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Liverpool-Lad

Certainly not normal, and obviously engine based.

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KenONeill

It sounds rather like it's dumping boost under high throttle conditions to me too. A very careful investigation of the plastic pipes and joints seems indicated.

stuartg40

Cheers for the replies so far. Just to clarify though (I'm new to all this) do you mean the boost leakage would cause the jolt? If so, why do I only get the jolt when coming off the gas/reducing boost pressure and why do I not feel it at all if it's just been at maximum boost pressure?

Thankyou gents,

Stu.

KenONeill

Ah, that doesn't sound so likely then.

razor

Its ur D.V happend to mine,all u need is a better D.V ie Forge...not the Crap plastic Bosch job it has now.the DV cant take the Higher Boost levs as smoothly as A After market DV

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stuartg40

OK, thanks. I thought it might be something to do with the DV, but I discounted that as an option when it seemed to do a great job at max boost - my logic was that if it wasn't up to the job it would be failing at max boost pressure and not just when ur throttle is just open a bit. Anyone else had this problem? Any recommendations on which DV gives both reliability/lack of engine management issues and good sound? I don't want anything deafening, but a louder whoosh would be nice.

Ta,
Stuart.

Goochie

My old Ocatvia did this after a remap by a "reputable" company from a flat part of the country. Never did get to the bottom of it, even after changing nearly all the hoses and checking all joints etc.

I posted a thread about it some time ago (possible nearly 2 years) where a number of people reported a similar problem.

ethos

I have the same thing, tempted to get the n75 changed...but dont want to start chucking money at it incase it isn't that.

baloo247

i sort of had this. my issue is more that i have momentary loss of boost after my remap.

i went back about 3 times to get it sorted. all the dyno information showed it was hitting 18psi and then dropping down to 14psi.

i replaced the n75 with a n75j valve, didnt help.then replaced it with another n75 becuase we thought the original might be screwed didnt help. so i replaced the DV .. that didnt help.

in the end we tracked it down to teh wastegate actuator. so i now have a release valve in teh pipe going from the DV to teh wastegate. unconventional i know but it works and im putting in a boost gauge to monitor boost pressure.

im probably going to take it to jabba at some point to get them to check the map and maybe redo it.

stuartg40

What's an n75 please people? Expensive to replace? I don't mind putting a bit of cash towards it but the Revo remap is £468 so that's enough really for 27bhp in my opinion! (plus the big torque gains of course). Should I go for DV or n75 or what? Would skoda be helpful or do they have a philosophy of not giving a stuff after a remap? What you said about the wastegate makes mechanical sense I suppose - anyone else had issues there?

Stu.

martziniuk

So does everybody find that you need to replace various parts/have problems on a standard octy after a remap, or is it just the luck of the draw?

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razor

Try a D.V first...it will benifit you any way as the dyaphram in the Bosch is plastic and isnt very Flexable to half boost etc thats higher then normal....a Forge Spilter will sound good and have better internals plus it wont throw up a ECU light.

Thats just my lot on it!

Hope it helps!

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mluton

I get the above to and also on changing gear, coming off the throttle.

Only started happening from having my remap.

Thought it was just the remap making my car act more aggressive / different.

Oh! I have an aftermarket DV on mine aswell.

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stuartg40

Jabba mention "lift-off lurch" as a consequence of less-than-ideal maps on their site. Does that refer to this maybe? I found this too...

"1.8T Billet Bypass Valve Kit: The Turbo XS Billet Bypass Valve Type 25 was specifically designed to replace 1 inch (25mm) Bosch Bypass Valve used in most Volkswagen Audi applications. The Bosch valve prone to failure in stock application not adequate for holding boost in "chipped" 1.8T equipped vehicles. The RBV-25 spring tension adjustable , making it ideal for your modified vehicle. The RBV-25 relieves pressure surge caused by changing gears or backing off throttle quickly."

Could that be describing this seemingly common problem?

razor

Ah ha ....so what the **** is it??????

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Stuart_J

A Remap will increase performance & this will show up the weakness in any parts, If everything is working perfectly then nothing will need replacing, if somethings worn a remap may well show it up.

Personally I believe you should always use a reputable tuner with a rolling road & have a custom remap to get the best from your car. It costs a bit more but you will achieve the best from your car & the rolling road gives you a true measure of performance increase. A good tuner will run the car up as std before its mapped. That will hopefully show up if the cars performing properly before they start & hi-lite any defects.

All these cheaper maps where they just plug in a lap top, download some map or other will generally make the car feel quicker but as others are saying it often comes with problems, the statement we tried 2 or 3 maps until we found one that works sums it up. Remapping should not be like this, the mapper should have a feel for what hes doing & be able to customise the map to suit your car & your driving technique if required.

Like most things in life you get what you pay for, people like Jabba might charge a bit more but you will know you are getting one of the companies that can give you the optimum remap & have a vast knowledge base to know instantly why somethings not right, they will often identify problems you hadnt even noticed. Its also not just BHP that matters, a good map will give the best mpg achievable with the performance gain, a quick fix when mapping cars to reduce the risk of overheating is to throw too much fuel in, solves the problem but knocks a big hole in the mpg, something most people wouldnt even have thought of, with Diesels some maps going just for performance will go for max torque as well, most good tuners shy back from this as they know that little extra bit of torque will end up eating the clutch & possibly worse, transmission parts a few months down the line.

If you can afford it go with a reputable tuner like Jabba. Cheap might be cheap but how much more will you spend sorting the problems afterwards & how do you know that the claimed figures have been achieved

Put it this way. If you had medical problems & had to pay who would you choose, the cheapest Doctor or the best you could afford, the cheapest might come up with an apparent fix but how do you know it will last & not have any side effects

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KenONeill

- the positive with a generic remap is that is should force the mappers to be conservative in their peak fuelling settings (and advance).

ethos

I think APR generic maps etc.. are probably ok. It's the smaller companies that can't put the research into it that could result in a poor generic map.

Liverpool-Lad

All depends on the engine condition. Luckily mine had only done 45k over 5 years or so and Ive had no issues in the 9 months or so its been on the car.

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2001 Rally Red Octavia vRS...remap complete Whiteline rear ARB, Superpro dogbone bush - 225/45/17 Goodyear Eagle F1 Aysmmetrics and lots of V-Power!

Smiles all 'round

Snoopie

Clean the throttle body, and then re-align it.
Once remapped, if it's jolting, it would indicate more of a problem than when not.

ethos

Not sure if I'd feel confident cleaning the throttle body and have no idea how to re-align it!

Wouldn't mind getting rid of my surge, just hope it's not damaging anything.

N75 shouldn't cost much to get replaced at a dealers, £50ish I'm guessing?! Anyone had it done?!

Goochie

I was thinking about this thread last night and thought I'd add that with my old Octavia, there was a slight, hardly noticable dip in power that occured around the same RPM as the part throttle hesitancy. The mapper's rolling road produced a perfect curve but Marlin's independant graph showed a very slight dip in power at this point.

DGW

An N75 was priced at £56.44 a couple of years ago.

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Denis

2002 Octavia 1.8T 4X4 turbo Estate - rebreathed on by Jabba ... 31.93mpg
2007 Fabia vRS - CC, ESP and full leather trim by Seat Surgeons ...48.57 mpg...