Power Loose Problems after 5k RPM

[TwinTurbo]

Hi Guys

I am new here and hope I am making a correct post in correct section

problem:

I have Japan Legnum VR-4 Type-V. and testing with my brothers car (same VR-4) I noticed that after 5K RPM my car is loosing some power. can some1 advice me several problem resolution, or where should I start from ?

Thanks in advance

[swinks]

Hi! And welcome!

How is it to boost related? Asking 'cos might several different issues, i.e:
- dump valve leaking
- boost vacuum leak
- hard pipe leak
- turbos is dying
- fuel pump issue
- fpr issue.

Give more details, please.

[TwinTurbo]

Thanks for reply


so your suggestion is to check Boost first ?


I cant check Boost cos I dont have gauge installed yet, so I want to start with replacing Fuel Pump first. when I checked my brothers car torque after 5K is still increasing or keeps same. on mine one I can feel that car is dying abit after 5k. on a drag race bot cars run at same level with 1st gear, turning into 2nd and brothers car is in lead.

[Davezj]

personallyi would do the cheapest first abd start with a pressure test of all you turbo pipes. if you have a compressor it will only cost for a few fittings and a disk of wood/metal.

then get a boost gauge this is most usful gauge you will buy for your car. £20-£30 will do it.

this will help you check the first 4 on the list, not fully but it will get you started.

[TwinTurbo]

Ok Guys

Thanks for your help and prompt replies.

will gt back to you soon once I get my sellary and install Boost Gauge :)

cheers

[Turbo_Steve]

When were the spark plugs last changed?

I'd check your spark plugs and HT leads are good first: it's more likely it needs servicing than has developed a fault.

Then I'd start checking what the turbos and associated systems are doing.

It really depends what you mean by "lose power".

Buy a boost gauge. They're not expensive, and it's something the car should have had fitted as standard. It'll help you see what it is (or isn't) doing.

[TwinTurbo]

Thanks mate.

Regarding a Servicing, Car had run only 80K Km, I dont think that Spark plugs need to be changed, but I will remove several of them, front ones that is easyer to remove and try to photo them and put here. I hope you will find ot something from them.

in my coutry there is only several VR-4 (3-4) and only 2 legnum VR-4, so I dont thing there is someone who will help me phisicaly with this problem.

[Turbo_Steve]

If it's done 80,000km since the last time the plugs and leads were changed: I'd suggest you change them anyway, and get some colder plugs in there if you change them.

Unfortunately, if your plugs are breaking down, it's liable to be the rear ones that are in the worst condition.

Definitely get a boost gauge on there.

[TwinTurbo]

Car did overall 80K after it was manufactured

I got HKS Boost Gauge yesterday. now I need to plug it correctly.

anyone can shortly help me and explain where to plug it ? Boost Gauge is an used one and I dont have installation manual for it.

Thanks in advance

[Turbo_Steve]

There is a pipe on the back of the inlet manifold that it can be tee-d into: that seems to be the usual place to locate it.

How you get through the bulkhead is very much up to you:
Some people use the clutch-pedal blank, some people follow the wiring in through the side grommets behind the wings.

[TwinTurbo]

Hi Guys

Updates on this case:

I have just replaced Fuel Pump and unfortunately situation is same. there can be a problem with fuel now, because I am running on 95 Premium Fuel. want to check 98 now.

but it seems that there is a boost leak somewhere which is the worst case for now, because I have to check all pipes. tomorrow planning to install Boost Gauge.

Cheers

[TwinTurbo]

Hi all again

I have just installed Boost Gauge, here is the situation:

Standard boost is 0.2Bar, Max 0.3 in 1st Gear, After 5K boots goes down to 0.1 and even 0 Bar. and the most strange thing is that on Neutral when pushing Accelerator Boost gauge does not shows any positive preasure. Later I will make a video.

can you tell me what can be the problem now ? I suppose some boost leak.

Thanks in advance for answers and help

[elnevio]

In neutral under no load, you normally don't get positive boost anyway.

Boost leak looks a prime candidate - possibly even the dump valve is done for.

[TwinTurbo]

I even tried to Boost it up, with Manual Boost Controller. removed it from Boost Vr-4 running on 1 Bar. with same settings of Controller I hardly got 0.4Bar

[elnevio]

MBC will be of no help here, and unless there is a much more serious problem, this has to be a leak. Is your dump valve standard, or aftermarket?

[bradc]

It does sound like there is a big leak or your turbos are really lazy. Have you ever run it on fuel rated below 95 octane?

[Ghost_2008]

With the 95 Octane fuel your ECU will be holding back on the power to prevent knock....... this sounds like a leak in the air intake side of things....... check your pipework, start with the joints first as it may just be one is a little loose.... alternatively you may have a split in the pipe that opens under pressure, so you start to make +Boost, the split opens and you loose pressure. possible a leak from the intercooler....

This type of issue will drive you mad until you find out what it is, a friend of mine spent ages looking for a leak, eventually found that an intercooler pipe at the front had some damage.........

Are you getting any smoke? Obviously blue smoke from the exhaust will be the turbo's on their way out.........

An alternative to the leak could be the spark plugs, if you do remove them check thier spacing as the spark could be blown out..........

[TwinTurbo]

ok Guys

I've fixed it :)

the problem was with aftermarket Racing steel Air Filter. it was so jamed that that I could fill it up with Water. I washed it. installed it back and thats it. perfectly handles 0.45Bar in all gears, at all RPM. especially after 5K

so Thasnk to all for help

[elnevio]

Good stuff! :)


But 0.45 bar still sounds a touch low for a facelift Legnum?

[swinks]

Nev, are you gonna argue about 0.01 bar? It's within measurement tolerance. IIRC pfl have 0.44 and fl 0.46... But maybe I'm wrong. :coat

[Turbo_Steve]

Yes! Pedantry is what this club is founded on!

[Kieran]

Nev, are you gonna argue about 0.01 bar? It's within measurement tolerance. IIRC pfl have 0.44 and fl 0.46... But maybe I'm wrong. :coat

I always thought that 0.44bar was wastegate pressure, and that Pre-Facelifts boost around 0.55 bar and Facelifts at about 0.7bar.

[swinks]

You see Kieran... it's why I've put this: :coat
Obviously mistake wastegate pressure.