Is there something fundamentally wrong with the engine build
 

:(i have still have a big problem.

After spending 6 months and 3500 quid making my car single tub i (still) have the same oscillating boost problem i had on the standard twins on the brand new engine (3k) (which was partly why i brought forward it going single in the first place). The guys who built the engine where reluctant to solve the initial problem so i made the car single to get rid of all the associated boost problems.(long story)

When i go into full boost it will still not hold. i get a vibration on and off twice a second and the boost dips and rises constantly with the vibration.about quater/half a point I will try to post a video of this on youtube.

I am starting to think that there is something fundamentally wrong with my engine build. I say this because i have replaced everthing in the engine bay apart from the map sensor.

are there any pro builders here who can tell me the type of mistake in building teh engine that would cause this? its audible and you can feel it vibrate. yet the engine is still free revving and powerful.

I am thinking

a) rotors are not matched
b) eccentric shaft out of tolerance.

I do not know guys what would cause this?

Is it definitely related to boost? in second gear try revving the car slowly up to 5-6k rpms and stay out of boost, see if it does the same thing.

You've made no reference toward the standalone you're running. What ecu are you using and have you at least had it tuned? I wouldn't think a rebuilt engine would/should have any problems from anyone that knows what they're doing. I'm putting my money on the map you're running...

Im running a pfc with dataloggit, the twins ran on a map supplied by the guys who rebuilt the engine. this oscillation occured with this setup. i took it back they tuned it again but didnt get rid of the problem. i am now running a totally new map on my new setup. i still have the ones done by the guys saved. this didnt run a boost controller

The single has been tuned with a rich base map based on the same setup. i have leaned the map out so it runs safe afrs. also i have now added a profec b.

this oscillation only occurs when boost trys to hold. the car runs ok until the boost hold period on wot. it seems smooth. i am very puzzled.

surely it cant be the map causing this. i have ran a few. what settings could cause this?

i Have been advised it could be because my boost is set to sharp, so i will try to adjust this softer tonight. i will also try using different sources of boost vac.

I'd definitely double check your boost controller settings. which unit are you using?

Also look at the wastegate connections and fittings.

What happens when you run it w/ boost controller off?

What are your boost control values set to?

Feel free to post your map for critique as well.

you need to check for boost leaks.

maybe the intake manifold gaskets, or something like the egr valve, etc is leaking and the shop never looked for a leak, instead looked at solenoids/etc.

I really dont think it is something to do with your engine build.