Jump to content
SAU Community

Recommended Posts

Hi all,

I am having big over boost issues with my KKR 480.

If I disconnect my actuator so the waste gate is fully open the car still hits about 25psi at 5000rpm :S...

The turbo is fairly new and the wastegate isn't getting stuck closed.

It makes no sence... you shouldn't really see any boost when the wastegate is fully open.

I had this same turbo on my VS commodore and that didn't over boost.

First time I boosted it with the KKR480 in it I saw my AutoMeter boost gauge hit the stopper so about 35-40psi and it blew one of my silicone joiners inside out when I ripped my foot off the accelerator and this is running with the actuator hocked up with no boost controller.

Edited by Finny
Link to comment
https://www.sau.com.au/forums/topic/192546-stopping-overboost-with-iw/
Share on other sites

either the internal wastegate is too small, or your exhaust is too free flowing.

perhaps try a restrictor in your exhaust first, and if that fails, look at an external wastegate setup.

Yes my exhaust is very free flowing, Also jeff please read the tread before replying.

Problem is I want a low mount manifold because I just got my dump pipe and intercooler piping fabricated to suit the low mount but I am pritty sure there is no low mount external gate manifolds about.

I had the same problem as you man, turned out the dump pipe i had on my stock turbo wasn't the right size for the new turbo and the wastegate flap would hit the inside of the dump pipe when it opened and blocked it off. This ment that it would overboost something crazy just like you said. I ended up getting the wastegate pipe enlarged so the flap could fully open.

Disconnect your actuator and then open the flap and listen if it hits the dump pipe before it is all the way open.

Actually scratch what i just said above!

My car is still doing it!!! Went for a spin then with the actuator disconnected and still hits around 20psi!!

I had the dump pipe fixed the other day and the wastegate doesn't hit on it anymore so i thought it was sweet but after going for a test then its still doing it.

Looks like im still in the same boat as you buddy. So does anyone know what F***ing causes this??

Is it that the split dump pipe can't flow enough gases through the 1.5" wastegate pipe or what?

Dude KKR480s have a dump molded into the turbo so that its just got a V clamp back end. It is impossible to modify.

I got my waste gate bored out about 5mm all the way around so from about 20mm to 30mm and it made no difference, still boost spiking like crazy with the waste gate fully open.

Hmmm well i guess in your situation the dump pipe isn't the cause of it. I reckon in my case its the turbulance in the split dump in the place where it joins is that its not flowing into it and causing back pressure through the wastegate. This means that the exhaust gases go the path of least resistance through the turbine housing.

I might try to get an all in one dump pipe with no split, or just make mine into a screamer, which i dont really want to do....

  srf said:
I had this problem when i started tuning my ecu.

With the stock ignition map, the ignition is so retarded that boost is uncontrollable.

I fixed my ignition map and it was sweet.

Could it make it overboost that high from just the standard map :)

I have done some pritty mad tuning with my SAFC II so that this thing spools at 3000rpm I might disable my changes and see how it goes.

I also have maximum timing and a strait through 3" exhaust with a cannon, no mufflers.

I bored the wastegate out my self... but because I didn't replace the flap I bored it out about 1-0.5mm less than the size of the flap which is still a huge difference. I will bore it out further and change the flap and see how I go but I dont think its going to make any difference because the V clamp dump is too restrictive for a larger wastegate hole.

I really don't know why people say that the KKR 480 is a laggy turbo, my car is pritty much stock and it spools it before 3000rpm.

so can having a car running too rich and retarded make it overboost

Ive never heard of this before

It may be the answer to my problem

mine doesnt overboost by too much i can still rev to around 6000 rpm before it boost cuts

Yeah i've never heard of it either Pedro, doesn't really make sense how a car running on a rich and retarded map would somehow cause the exhaust gases to go through the turbine instead of going through the wastegate. At the end of the day exhaust gases are just basic fluid mechanics, go through the path of least resistance, usually being the wastegate when it's open. So to me, any major overboost problem is caused by the wastegate pipe no longer being the path of least resistance, wether it's caused by turbulance or something else?

Has anyone had a major overboost problem, not talking about 1-2psi and found a way to fix it??

This is from http://www.sdsefi.com/

"In severe cases of retarded timing, the mixture is still burning when the exhaust valve opens. Because turbochargers are driven by the energy in the exhaust stream, high EGTs caused by retarded timing produce so much energy at the turbine that even a fully open wastegate cannot control the boost pressure. All in all, retarded timing is counterproductive to producing an efficient, durable, powerful engine."

So at the retarded map with a very free exhaust the wastegate cant flow enough. I had 20psi with stock maps and went down to 7psi with a advanced ignition map. nothing else was changed

If you did have a larger wastegate that would solve the overboost problem as would having more exhaust back pressure.

  srf said:
I had this problem when i started tuning my ecu.

With the stock ignition map, the ignition is so retarded that boost is uncontrollable.

I fixed my ignition map and it was sweet.

how did you do it? (ignition map) manuali? or i can fix it by AFC NEO ?? ( i have afc neo) an if by afc neo what settings you did?

Na factory ecu tuning. the last load pont of the rb25det map for ignition is super retarded. If your hitting that point it would cause problems. I was hitting it on the rb25det ecu with a straight pipe and a intercooler.

Its just R and R which everyone goes on about.

Dont have a clue how to tune an afc.

If you bring down the afm voltage you could read of a lower load point i surpose?

Edited by srf

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I'm hoping I just don't have to do an engine rebuild NOW. Doesn't mean I won't do it at some point. I think a plus point is that the car presumably ran on or close to stock power nearly all it's life so far. Only the Owner I bought it from actually increased power with a standalone ECU and blew the OEM turbos. And after it got thee 2860s it wasn't driven an awful lot either.   That is what I meant. With the twins coming on so late (4500-5000rpm) I hope the rods won't want to exit the block prematurely. And it still being a 26 means the torque curve isn't gonna hike up all that much.   It didn't blow up on the dyno when they tuned it to 500ish crank. So I suppose it'll be okay for now. They did put a Tomei head gasket on first though which did not seal at all, and they redid it with a Cometic one. Which I hope won't be my water leak.   Mainly anything oil. So far all it has is the N1 pump, oil restrictor and a filter relocation kit with a cooler.
    • 15000? ish? Something like that anyway. It wasn;t so much a wear as a tear that then spread. Might have lasted a lot longer if not bothered by just one incident, whatever it was. I took a punt. They are really comfortable and do a good job of holding. My daughter HATED it when I first put them in, and probably still does now. She has sensory issues and hates the way they are all up your business. I'm 197cm and 95kg. Not fat or particularly wide, and the XL size seat is the rigth fit. If I was any fatter it would start to get too snug. Any skinnier and you'd possibly want the smaller width.
    • Mrs rs focus came factory with recaro cs  sportsters in it and they a pain in the ass to get in and out of with the really high bolsters, once you were in them they were one of the most comfortable seats I have ever sat in
    • The NA 2.5 has very little torque. You won't feel much. Those trannies are also a million years old now and it could well be f**ked. First generation electronically controlled autos will often refuse to kick down, ete, etc, depending on what's wrong with them.
    • Yes, but no but yes but no. Those "it's fine up to 500HP" rules and everything else like it were all determined back when the cars were 10 years old. As they are now 30 years old.....what do you reckon the chances of something shitting the bed are? I'd say they are much higher now than they used to be. You might be lucky. You might be unlucky. Spin the wheel and find out. Yeah, nah. It's actually exactly the opposite. Making boost early and having heaps of torque able to be generated right in the middle of the rev range will do more to damage an engine than having to rev it high to make the power. Think about the load on the conrods, bearings, etc, to make 400HP at 4000 rpm, vs 400 HP at 6500 rpm. So someone has already "let the Nissan out" which is how we describe the increased chance of a fiddled with engine to have had something done wrongly. Many more engines that have been opened die than stock ones do - even if you into consideration how they are treated wrt power levels and the like. Again, not saying that yours will definitely have been put back together by a moron. But the possibility does exist. It's still a lottery. Spin the wheel. What weakspots?
×
×
  • Create New...