Thread: Query on setting up turbo on NA 4BD1

Originally Posted by The Mutt

So what amount of boost can I look at getting from my turbo without going over the top? We will be towing a large sailboat on a regular basis, at other times the Rangie will be topped with a ShippeShape and the back loaded with gear.

Glenn

The main issue is keeping EGTs down. Fit an EGT guage and set it up based on that.

Stock (4BD1T) boost is 16/17psi. <20 is probably fine. But whether you can achieve that depends on the turbo and fuelling.

Originally Posted by isuzurover

The main issue is keeping EGTs down. Fit an EGT guage and set it up based on that.

Stock (4BD1T) boost is 16/17psi. <20 is probably fine. But whether you can achieve that depends on the turbo and fuelling.

The 4BD1T that I fitted came from a truck and the turbo only boosts to 9psi max according to my gauge. I was led to believe that standard boost was even less than 9psi, so I have'nt 'played' with it. 16/17psi sounds more appealing. Are these figures mentioned in an engine manual anywhere ? I would like to try more boost, but one of my main aims is to get a long life out of my engine.

It's interesting to see that a company like Turbo-Glide set their turbo kits to 9psi.........

Q. How much boost and power do you set up for along with Max EGT?

A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.

Turbo-Glide: Turbo FAQs

Originally Posted by rijidij

The 4BD1T that I fitted came from a truck and the turbo only boosts to 9psi max according to my gauge. I was led to believe that standard boost was even less than 9psi, so I have'nt 'played' with it. 16/17psi sounds more appealing. Are these figures mentioned in an engine manual anywhere ? I would like to try more boost, but one of my main aims is to get a long life out of my engine.

It's interesting to see that a company like Turbo-Glide set their turbo kits to 9psi.........

Q. How much boost and power do you set up for along with Max EGT?

A. We use 9lb and a torque gain of no more than 30% and an EGT of no more than 500°Celcius under prolonged full throttle usage. My staff and I have seen many turbo kits installed exceeding these parameters resulting in severe engine damage. Use of chassis dyno is mandatory before and after fitment of turbo.

Turbo-Glide: Turbo FAQs

Someone (maybe Isuzurover) found factory figures of around 13psi. My 4BD1T turbo wastegate was set to about 20psi, not surprisingly it never opened until I cut the arm and welded in an adjustable section. It was doing about 18psi max back then, but didn't need it. Dropping the boost to 15psi gave it more top end (if you call 3000-3600rpm top-end) and gave me EGT's of about 600C at full load and moderate revs. I could get them up above 700 by red-lining it.

I suspect turboglide are basing their 9psi on their experiences with fragile stuff like toyotas with indirect injection. Their figure of 500C suggests post turbo.
With 9psi and a boost/backpressure ratio of 2 (what I get under acceleration) that gives you a preturbo EGT of around 630C. Plenty hot enough for many IDI engines.

Boost by itself does not hurt an engine. It's the combination of boost, fuel loading and injection timing that determines the stress on an engine. It's possible to put a lot of extra stress on and get little extra power if you're doing it wrong.

I've been running 20psi with no intercooler and EGT's to 750C (occasional accidental excursion past) for just over a year now. 12,000km.

I 2nd what Dougal posted.

They probably had in mind the indirect injection toyota and nissan engines. Indirect injection engines typically have compression ratios about 22:1 to aid starting in cold climates.

The c.r in a 4BD1 is more suitable for turbo engines.

Originally Posted by Bush65

I 2nd what Dougal posted.

They probably had in mind the indirect injection toyota and nissan engines. Indirect injection engines typically have compression ratios about 22:1 to aid starting in cold climates.

The c.r in a 4BD1 is more suitable for turbo engines.

More suitable? at 16:1 it should NEVER of been naturally aspirated

Originally Posted by rovercare

More suitable? at 16:1 it should NEVER of been naturally aspirated

I've seen figures which go right up to 17.5:1. The highest compression ratio I've seen on a direct injection diesel is 18.something.

Unless you want to look at Scanias ethanol burning diesels, 28:1 static with a decent amount of boost on top of that.

Thanks guys, I came across info a while ago saying that the factory setting for the 4BD1 turbo was 5psi and never go over 12psi, it is going to be interesting to see what I can get out of this engine/turbo setup.

Firstly I'll get our Rangie back on the road with the Isuzu running a basic setup, iron out any bugs from the conversion then start to tweek the settings to improve performance, this is going to be interesting.

Thanks Again Guys ............ Great Forum

Glenn

Originally Posted by The Mutt

Thanks guys, I came across info a while ago saying that the factory setting for the 4BD1 turbo was 5psi and never go over 12psi,

Name and shame.