right im really getting ****ed off with my vf35 hesitation and im determined to find out whats causing it....

my car is a wrx blob that was fitted with an sti8 bottom end and wrx heads,i had it fitted with a vf35 bought from matty on here and i had it mapped @ rcm on their dyno by duncan race dynamix.

the car made 354bhp @ 1.45 bar but sadly the car big-ended on the dyno so i never got to drive it.

i bought a sti8 long engine from matty (from the same car that the turbo came from) fitted it with new timing kit/oil pump/seals etc etc and i had duncan out to tweak the map to suit the new engine but ever since this new engine has been fitted the boost problem has been there.

i dont think it was there before as duncan would have noticed it during mapping,so between swapping engines it has happened.

it boosts fine in 1st and 2nd but 3rd/4th/5th @3800 revs + it sort of hesitates and it makes like a pft pft pft pft pft (sort of flutters)noise and basically the engine struggles to pull through it-if i feather the throttle ie back off slightly then re-apply it doesnt do it and pulls like a train to the redline.

it also doesnt do it if im slowly taking the car up to the 4k rev mark-its only when im driving it "enthusiastically"

ive had duncan look at it a few times and there is nothing in the map that suggests there is a problem,he even turned the boost down to 1.4 bar but it still happens.

the full spec of the car is this (nothing has changed from the original mapping session apart from the engine itself)

rcm headers/venturi up-pipe/3" bell-mouth de-cat japspeed downpipe all heat wrapped

3" de-resonated de cat center section from scoobyworld

afterburner raptor backbox

rcm induction kit with scoobyworx silicone airbox hose/intake pipe

rcm 340 fuel pump

sti top mount with oem dump valve and sti undertray

650cc flow matched injectors from cannon fodders old car fitted with new seals

sti inlet manifold-tgv delete

ngkpfr7b plugs

vf35 turbo-non ported came from a 75k ppp blob sti

sti 8 long engine from same car as turbo-avcs is NOT running as i havent wired it up

standard fuel pressure reg altho i have a 3 port fuelab to be fitted next week to cure a fueling problem as the car is struggling to start from cold and when warm it gives off black smoke when started

the engine is a gem,it uses no oil/water at all.its been in 6 months now and i havent had to top it up once

i have been given various answers as to whats causing it.......

cavitation

surge

its because im not running the avcs

silicone intake pipe may be causing irregular airflow at high rpm

maybe fuel pressue related as they can cause hesitation when faulty

does or has anybody had similar problems?

im about to start getting parts for a 2.1 stroker but i will be devastated if when i come to have the new engine mapped that the problem is still there should it not be turbo related

any help guys as this is really causing me not to enjoy the car.

surely if it was turbo related it would have done it on the original engine and during the mapping session?

heres the engine that big-ended



heres the engine i have fitted now



heres the power graph etc,as you can see the turbo pulled strong and made awesome power for a vf35

 

id start a thread on what works on your car it would be far shorter lol

 

oh

 

does anybody know the correct restictor pill size for a vf35?

 

quite honestly mate i dont know why you persist with it, its a bag of problems. even if you do get it all finished with a 6 speed and stroker in it the cost will be stupid for what you have got.

id cut your losses as you cant enjoy owning a car that has so many problems.

 

haha i see what your saying but the car isnt a bag of problems,it only has this boost problem and the fueling problem and that is all

everything else is fine on the car gearbox/clutch/steering/brakes/suspension

its just 2 niggles that im determined to get to the bottom of

 

Hi Mark

I would speak with Duncan or mapper of yours choice and I'm sure he will get to bottom of it

Its does sound of it like momentary(split second) fuel/boost cut to me,have something similar when we run on WRX engine(on non stroker) LPG

Jura

 

would that be something to do with the ecu?

 

I cannot say for sure its mapping or ECU related,but can be too surge(boost creep) on the VF35,they're known for this and usually how you can solve this,is porting the wastegate,I think Big D done on his turbo this mode and his turbo made nice numbers


Jura

 

if it was surge tho wouldnt it have done it on the previous engine aswell?

 

Yes you should have surge on previous engine if spec of the car is the same,but I wouldn't rule out this too

Jura

 

Have you checked plug colours?

 

???

 

he means to see if they are light brown/tan so you know they are firing correctly

 

Checking them today when I have the compression test done mate

 

i doubt its spark plug related anyway

 

Check colours i had similar prob then I noticed it run rich on one bank. Where's Hinckley based?

 

Between Leicester and coventry. The plugs were new when engine was changed

 

Mine does a similar thing in terms of noise if I'm in 6th at low revs and put my foot down it sort of flutters still seems to pull ok though!
After I heard it I stopped doing it until I got my gauges fitted! Turns out the car peaks at 1.5 however when in 6th at low revs with foot down boost rises to 1.7

 

Inlet pipe sucking shut a little?

Coilpack or plug misfire?

Whats the boost gauge do?

 

It is related to the VF35 and the silicone inlet pipe / induction kit - they are prone to surge. A solid pipe (or std one), porting the wastegate or turning the boost down will solve it as discussed before Matt.

 

So its compressor surge not hessitation?

 

Any ideas why it didn't do it on the mapping session dunc on the original engine?

 

sorry to jump in but did you find out the pill hole size for a vf35 shreksta? thought id ask seeing as simon and duncan were on the thread. my sti had the pill missing so used a 1mm welding tip in place of a pill and its boosting to 1bar now and pulling like a train. just wondered if 1mm was the correct size for an sti? its a 2002 bugeye sti with vf35 btw.

 

think its nearer 0.8mm

 

cheers simon, so would it be worthwhile getting another one at 0.8 and installing it? maybe see a bit more boost? car has paperwork for an ecutek remap to 300bhp so i,d have thought it would run a bit more boost? my old wagon ran 1.3 bar at 315bhp.

 

yes but worth considering getting it checked as if it was mapped lower for a reason you could damage it

 

ok thanks a lot for the info. how much is a remap with the licence already on the ecu simon? pm if you prefer thanks.

 

£360 but more than happy to add restrictor pill and check it and advise whether a new map would actually gain you anything.

 

sorted cheers guys,swapped the silicone intake pipe for the oem one today and its so much better

there is still a very faint trace of surge in 3rd and 4th @4k rpm but its hardly anything and the car pulls straight through it where as before it would just hold back,im guessing some porting on the turbo will help that last little bit

feels so much better now that i can keep my foot planted in 3rd/4th without having to back off,i guess the vf35 doesnt like a silicone intake