Vnt

[Stanley]

Hi Guys, i meet a couple of you at pod last week and joined up. So my renault 5 has a vnt on it, apparently is one of the original turbo developments ones. Ive had it rebuilt at universal turbos. How do i tell what type of actuator is on it? At the minute it seems to start spooling around 2500rpm then full boost by 3k at 0.8 bar of boost. What sort of boost do these perform well at? cheers

[Ian S]

A pal's 5GTT, C1J engine, with a lot of head work and raised compression, made 244BHP at relatively low boost, not now sure what as that was back in 2004 or so, maybe 20PSI.

That was from Jim / CTM not Turbo Developments. IIRC, there was a slight difference in turbine wheel or housing size.

As far as actuator, Jim tended to use big ones, but not always. The spring strength, diaphragm size, spring pre-load, all factor into the boost setting. There weren't that many VNTs and they all seemed to be a bit individual. If they still in business, maybe you'd have to ask Turbo Developments if they made different specs and check the receipt / spec sheet supplied with yours.



Also, have I sent you a membership card? My SSD failed a couple of days ago and I have no records of recent stuff.

[Stanley]

Hi Ian, thanks for the reply! yes ive got me card. Is there anyone local ish who could help with setting it up ?

[Ian S]

There's one current RTOC member in Southend: https://www.rtoc.org/boards/member.php?8447-Pukka

He joined last year, but he 5 is a race car. So maybe he might be able to assist you in some way. You could send him a RTOC Private Message and see if he responds. He is the one who was going to Santa Pod last weekend but put his tickets up for sale and went to Le Mans instead.

You can search for members by clicking the 'Members' button in middle of the bar under the logo at the top of this page, which goes to this page: https://www.rtoc.org/boards/memberlist.php

On the upper right is 'Search for members'. Click on 'Advanced' and you can search in locations.

There have been a few members in Southend but they've moved on or won't pay to join and use this clubs facilities.

[Matt Cole]

Vnt's have always been notoriously hard to set up, great if you can get them to work. The vane lengths needs adjusting to the tune of the carb and then setting up to avoid overboosting.

[tubbyG]

I also have one of these VNT's on my 5. Although a little tricky to set up they are fantastic turbo's - I love the adjustability they bring. I am no expert but I would say they are ok for 20+psi dependant on the spec of the engine fitted onto.

What boost level was the car set at prior to the turbo being rebuilt? and do you have any way of listening for det?

Do you have any adjustability on the TDC pickup or aftermarket ignition?

I have specced my carb to allow for fueling over 20psi. The way I have set my vnt was as follows:

Set the vane position so that boost comes in a little later in the rev range, then adjust the actuator to increase boost untill I was happy with the afr in 4th @7k rpm - So max boost set.

Then I started adjusting the vane position untill the boost was coming in earlier, keeping an eye on afr's. I then adjusted the preload on the second stage diaphram to richen things up a bit while under load. Once I was happy with that then I would have to then adjust the actuator preload again to re-set to the max boost (adjusting the vane position for earlier spool caused a reduction in peak boost for me)

In addition, I am running an external wategate which essentially just catches the boost spike which occurs just as the actuator is pressurised so I also had to adjust the gate opening pressure to just above max boost.

I also experienced some compressor surge at part throttle when I was setting up. This was due to me attempting to have full boost as early in the rev range as possible spooling at 1500 rpm with 23psi @2000 rpm so I had to raise that a little.

Mine is still a work in progress as I need the ignition fine tuned, and I am still quite rich on max boost. But will be worth the effort once I am done.