loosing boost

portland2002

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Points
31
Location
uk portland
Car
seat leon cupra r
just tuned my seat leon cupra r bam engine.had the k04 turbo rebuilt with a larger compressor wheel complete engine rebuild inc intergrated engineering con rods.with full exhaust system inc tubular manifold and new n75 valve f type.when took it to get mapped on a dyno it holds 1.5 bar boost upto 3700 rpm then drops to 1.1 bar then on.even when dialed in 1.5 bar it will no hold it i think maybe weak actuator? i have checked for boost leaks tight as a drum anybody got any ideas?. power figures were 292 ftlbs at 3700rpm and 262.4 bhp at flywheel
 
262.4 bhp seems quite a lot for a 1.4 16valve :blink:

Have you double checked your vacuum hoses to see if any are collapsing buddy? I had this once and went for a silicone tube version with thicker walls.
 
the bam is a 1.8 the same as my leon;)

Is the f version the standard type n75? Cause I know certain versions can cause spiking if you're using a non standard 1
 
boost not holding is often a pipe that is loose, split , or not up to the job .If those are ok then I would look at the split actuator.next..

A point though - Clearly you have raised the boost a fair bit so it could be that what was fine is now not up to the job,
A pipe could be fine at 1.1 but not at 1.5 there is a fair difference.
Also how are you measuring the boost as gauges often dont read correct especially if it is a manual gauge ( not electronic) This can be because the pip[e run is very long or the gauge isnt good enough. Also you need a decent boost controller and of course it hads to be correctly set up
 
Sorry my mistake. Herb is correct. They are a 1.8.
I always thought they was 2 litre :blink:



They share the same engine as the Audi S3, Audi TT 225, Seat Ibiza Supra R and ofcourse the Leon Cupra R. I maybe wrong but I think Skoda used the same engine in the Octavia VRS petrol version.
 
:embarrest: Thanks TN, I merely looked at the OP's car listing under his name and saw 1.4 16v and thought he must be some kind of witchdoctor to extract that kind of power from it :lol:



There is a guy known as Drew on the Rover forums who has a 1.4 that's pushing over 300bhp! It's in a Metro too! :lol:
 
262.4 bhp seems quite a lot for a 1.4 16valve :blink:

Have you double checked your vacuum hoses to see if any are collapsing buddy? I had this once and went for a silicone tube version with thicker walls.

yes took it to aed advanced engine dynamics in wyke regis they have done a smoke test no leaks. i have changed the n75 to a j type fitted a forge actutator with a 24 psi spring fitted. the turbo has been totally rebuilt again this time with a mitsubishi comp wheel its goes like stink pulls 1.5 to 1.6 bar upto 3700 rpm then still drops back to 1.1 bar. i am beggining to think its maybe the ecu being over protective? also a forge 008 dump valve
 
Last edited:
262.4 bhp seems quite a lot for a 1.4 16valve :blink:

Have you double checked your vacuum hoses to see if any are collapsing buddy? I had this once and went for a silicone tube version with thicker walls.
no all silicone inc tip so ruled that out
 
How is the boost actually being set/controlled and what ecu is in the car.
stock ecu but remapped hits 262.4 bhp at 3700 rpm and 292 ftlbs torque which is great. but instead of the torque curve climbing and starting to drop at about 5800 rpm like it should. you on the dyno readout a wavey line where it trys to hold 1.5 bar then drops to 1.1 bar then up to 1.5 for a split second then drops down to 1.1 bar again all the way to the redline.if you were driving it upto 3700 rpm climbs really great giving 1.5 bar upto then after that its still goes but feels flat ecu controlled by n75 valve j type
 
There is a guy known as Drew on the Rover forums who has a 1.4 that's pushing over 300bhp! It's in a Metro too! :lol:

is drew still about then i very nearly bought his 1.4 k series turbo engine back when i owned my mg zr.

just as a side note im running 230bhp out of a 1.4 8v pushrod carb fed engine and possibly more which we will find out this month. i also know of a proper genuine same engine without nos and still on the carb making 286bhp.
 

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