Jump to content
SAU Community

Recommended Posts

Matt Tang was telling me his vcam RB28 would push the -5's into surge occasionally. A combination of the added displacement providing a little more exhaust flow than a 26, and vcam inducing more overlap to to gain more mid range torque earlier in the rev range. The advice I heard Racepace gave Matt was that the surge could be tuned out, but at the expense of low end torque, most likely making the vcam retard the intake earlier.

So what we can take from this is that if your engine is optimised to the limit, even -5's will push into surge.

(I'm talking surge here, not shuffle... don't confuse the two)

My -5s will surge only on a 5-8 degree morning, full load in 5th coming onto boost. Could be tuned out if i really wanted as you said, any warmer and it was fine so it wasnt a problem. It was more conditions than anything else - such a rare thing that happens maybe once/twice a year.

What is the difference between shuffle and surge as I am not aware?

Same thing, different words

In your case Ash they'd retard the ignition which would make more doey to drive when its hot, and not as fun when its cold...I'd rather have surge than shuffle.

Shuffle can be seen on a data logger when the airflow values read from your twin maf sensors wildly fluctuate. I had big problems with this at around 1800-2000 rpm with my GTRS's as they start making around 0.4kg/cm under full load at this speed. However as exhaust flow isn't enough to spin the turbo's up to wastegate opening speeds, and the engine is running in a vacuum at the throttle bodies the effect is that one turbo will spin up and stall the airflow into the other. Once this happens the exhaust pressure in the stalled turbo swings the shuffle the other way. The GTRS's suffer for this because the compressor is too big for the turbine.

This is why a HKS balance pipe exhaust manifold helps dampen the effect. Also it explains why the split/baffeled twin turbo pipe helps so much, as it allows air velocities out of each turbo to be established before mixing them back into one air stream before the intercooler.

For me, I still get shuffle if I stand on the throttle in 4th at 2000 rpm. It will shuffle (till full boost at 5000 rpm), where exhaust flow and back pressure is sufficent to overcome the shuffle effect. You can drive around this though as really you'd drop back to 2nd or third anyway if you wanted to go faster.

Surge won't effect response, in fact surge is the result of too much response (for a given engine speed). The turbo's are being over driven by exhaust gas flow for a given engine speed. The rate of airflow into the engine (from the filters to the intake valve) is below what is the optimal air speed for the given compressor speed. The effect is your turbo makes terrible sounds as the airflow stalls out and bleeds back to the intake of the turbine housing, which can lead to turbine damage.

I hope that makes some sense. Im operating on minimal speel and 2 glasses of red at the moment...

I'd argue the point of surge not hurting response, if its bad enough it can basically have the car "stall" at a given point in RPM until it pushes through.

If low enough in the RPM this can take quite a while.

When i can get mine surging, low rpm/5th/6 degree ambient - it will not go past that RPM point at all even if i hold it there for 10 seconds. I have to drop back to 4th, pass that RPM window (about 300rpm) and then it's fine.

They way I understand surge is that airflow stops because it cant go anywhere, except bleed back out the turbo inlet, so would I be rightin think that airflow stops or even reverses to an extent?

I remember my old highflow would surge like crazy at around 3000rpm in 5th when cruising down the highway, send the PFC Haywire and the motor would cough and splutter then clean up for a few seconds and repeat

could hear it surging a mile away...like a Chappel st VL lol

driving down the highway going tutuutututut constantly

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

    • The answer is to get a hold of the wiring diagram, work out what voltage is supposed to be where, when, and then work out why it is not there, then. I can't speak to the HR34 stuff, because I have never paid any attention to the NAs. There is a possibility that the turbo diagram will help, but it could also be different - depending on whether there is an FPCM on the NAs.
    • Hey guys. New here. I am having an issue with my hr34. The fuel pump isn't turning on. I removed it from the tank. Bench test it. Wasn't working. Order new one and installed it today. Still not turning on. Checked the relay. Relay has voltage on the contact side. I jumped it and it tuned the pump on. Which lead me to checked the coil voltage.  Turned on the ignition and had my meter across the coil and there wasn't any dc voltage. Had my meter lead on the positive and I used the frame ground and noticed there was 12 volts. Which lead me to believe the relay isn't getting a negative signal. I traced the wire ( black with pink strip).it goes back to the bottom on the steering and it gets lost into the harness.   I checked at the ecm and I can't seem to find that wire color.   My question if any one knows is. Can I not just run the negative through a ignition relay to turn on the fuel pump relay?. Or anyone ever had this issue and if so how did u go about fixing it.    
    • So many people don't notice it, as batteries decay slowly over time. Two big reasons people end up noticing and needing to replace batteries: 1) The cold weather. The cold not only makes it harder to turn the engine for a few reasons, but it also increases the batteries internal resistance. So this means you need MORE power to turn a colder engine, AND the battery has a lower limit on how much current it can provide. 2) Something gets modified/altered/added in the wiring, typically an aftermarket accessory, like a dash camera, or an alarm etc, and this adds a small amount extra onto the battery, and pushes it over the edge in its failing days. But if you hadn't have read this thread, and just pushed through, chances are you might have made it through this winter, just. But come next winter, it would have been kapoot. But the fact you changed it out now, means you've instantly noticed how much nicer it is for starting, and will be less worry for you that the engine won't start now.
    • Holy shit, I'm glad you brought up the battery issue and I'm glad I asked about measuring it. Old battery was at a healthy 12.82V in the morning with the car turned off. Removed the fuel pump fuse, clamped the multimeter on at min/max/average and cranked for ~3 seconds. It dropped down to 8.30V. So yeah, not surprising it struggled that much. Picked up a fresh battery from supercheap and it's ridiculous. Haven't done a cold start yet, but man, even with a warm start the difference is night and day. I can't believe I lived with this for so long. Just blamed it on it being an old modified car. Went with Century because convenient. If they are shit it'll be a future me problem. But just in case I set up a reminder for 30 months - 8 weeks to check on the battery state and get a warranty replacement if necessary. 
×
×
  • Create New...