1HD-T AFR results wanted

[David60series]

Hi,

Can anyone who has recorded AFRs please post their readings for 1HD-T?

In particular I am chasing standard CT26 without intercooler.

Can you please indicate if the readings changed over the rev range when at full load and full boost?

Thanks

 

[mudgudgeon]

Best bet is read through the "official 1HD-T tuning thread".
It's a bit of a how long is a piece of strong question. There's lots of variables.

 

[mudgudgeon]

Readings will change constantly as rpm and load and boost and fuel delivery are infinitely variable and inter-related.

 

[David60series]

As stated I am talking FULL BOOST and FULL LOAD only from those that have measured it either on road or on dyno.

I have read those posts before. Does not answer it. Mentions AFR but not in relation to rpm or if the vehicle is intercooled.

 

[mudgudgeon]

Yep, but full boost, full load will give different conditions depending on RPM too.

I might be wrong, but I don't think full boost full load will necessarily show the same AFR at 2000rpm, vs 4000rpm

Exactly what do you mean by FULL LOAD?

 

[Imwhere]

Are you talking wastegate pressure when you refer to full boost?

AFR will likley get richer as the revs rise as after 3000rpm the factory turbo chokes at wastegate pressure.

but AFR will vary wildly depending on the tune and condition of the pump

What are you trying to work out?

 

[David60series]

Gents, thank you for the responses. Much appreciated.

Full load - I'm considering to be WOT sustained from as low in the RPM as possible at full boost. Ideally on an incline if on road. I.e making engine speed attempt to accelerate.

Full boost I am considering to be the known maximum at the inlet manifold.

What I am trying to work out is what you have just alluded to; the variation in AFR over RPM on a 1Hd-T and what is 'normal'.

I am seeing AFRs get rich from ~3000rpm and also seeing boost drop about 1psi at this point. As you say, this is indicative of an airflow restriction but I have ruled out any leaks or physical blockages. I have 11psi max dropping to about 10psi.

I see richer AFRs from about 2300rpm onwards but more pronounced at 3000.

Starting to assume that this range is off the map for a standard CT26?

People say 'I run 21:1 AFRs' but I cannot see how you get a steady AFR on the stock set up.

Injectors and pump in good (overhauled) order.

 

[Imwhere]

No worries mate.

You are just seeing the restrictive factory turbo. The 12v 1HDT has the smallest and most restrictive turbo of the 1HD lineup.

Those other people are probably running aftermarket turbos which flow a lot better and can maintain air speed up higher in the rev range.

2300rpm may be where your aneroid is hitting max fueling and 3000rpm is your turbo reaching its choke point. but that is only a guess

Im at 14psi @ the inlet @ 1800rpm and the intercooler inlet is very hot after a run which would indicate its at its limit.

 

[mudgudgeon]

People say 'I run 21:1 AFRs' but I cannot see how you get a steady AFR on the stock set up.

That's just it. There is no "steady AFR".
It varies and changes continually on every engine.
You need to tune for a peak AFR and/or EGTs that are safe.
A reference to an AFR of 21:1 is a peak (or worst case) that you would see as you come off idle, under load, and before boost has built to a peak.
In this situation, you're dumping bulk fuel in to get the turbo to spool, but the turbo hasn't spooled up yet, so you haven't got the increased air charge volume yet.
As boost builds, and air intake volume increases, AFR will lean out.


And yeah, the stock turbo will be dropping off around 3k rpm.

 

[Imwhere]

Yeah would say its very hard on a stock setup.

21:1 would be a safe tune at full boost. and as long as you have a turbo able to maintain the set boost and flow until the govenor starts to pull fuel you should in theory be able to hold a steady AFR once at max set boost.

thats the east part getting the pump setup so its not too rich in pre-spool and with a nice ramprate thats matched to the turbo is the hard part.

Some people tune very rich, down to 12:1 AFR in pre-spool which should bring the turbo on hard and fast but will be very smokey. Its all a balancing act. But im no expert.