The Official 1HD-T/FT Fuel Pump Mod Tuning Thread

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So here's a few teaser pics of a 1HD-T custom, balls out pump I am building.
I wont tell you whats in it just yet, but you can certainly expect that I will, once it's tested and verified on a running engine.

download_20140906_201112.webp
download_20140906_201116.webp


It's mostly Toyota/Denso parts, but a little Bosch and a hint of Cummins added for a robust full bodied flavour.


There is no secret to these pumps that set them apart from any other VE rotary. The same mods that are well known in the Cummins, Volkswagen etc. can be applied.
Ill have to leave it at that for right now, dinner is awaiting.
Rest assured there is more to follow soon.
 
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What is the experts opinion?
Many 1HDTs seem to fail in cylinder 5/6. Anything from head, to head gasket to cylinder/block.
Neither the 1HZ nor the 24V 1HDFT have this problem.
Is the 1HDT with its poor flowing head not suitable for too much fuel and air?
Honestly, at this point I would take a
1HZ over a 1HDT anytime.
Cheers
Jan
 
The 1hdt and the 1hz head seem to be very similar in design for air flow. They also have seeming identical plenums. Do the gaskets fail at 5-6? Pistons burn holes? What exactly is the common failure on those cylinders? If it is an air flow issue, why doesn't cylinder 1 fail?
 
Jan-78FJ40 said:
What is the experts opinion?
Many 1HDTs seem to fail in cylinder 5/6. Anything from head, to head gasket to cylinder/block.
Neither the 1HZ nor the 24V 1HDFT have this problem.
Is the 1HDT with its poor flowing head not suitable for too much fuel and air?
Honestly, at this point I would take a
1HZ over a 1HDT anytime.
Cheers
Jan
Click to expand...

More valves do not necessarily lead to an increase in flow. VW is a good example...the 16v heads flow better than the 20v ones.

Based on the power differences in built HD-FT's and HD-T's I wouldn't be surprised if the difference is negligible.
 
I believe its mainly the plenum design that leads to cyl 5 and 6 running hotter than the rest. Similar issue on 6BT 12V and 24V. The intake is part of the head has basically no intake runners and 1 and 6 are the furthest from the air source.
A common fix on the Cummins using a P7100 inline is to set those two cylinders slightly lean at the pump.
The fix on the HDT would be a custom intake with larger plenum and tuned length runners, and additional porting in the problem cylinders. I haven't seen one with the intake off first hand, so I couldn't say if there's a sharp transition on those two cyl causing a slight restriction.
I ve always thought the HDT stock intake was a joke though.
 
Jan-78FJ40 said:
What is the experts opinion?
Many 1HDTs seem to fail in cylinder 5/6. Anything from head, to head gasket to cylinder/block.
Neither the 1HZ nor the 24V 1HDFT have this problem.
Is the 1HDT with its poor flowing head not suitable for too much fuel and air?
Honestly, at this point I would take a
1HZ over a 1HDT anytime.
Cheers
Jan
Click to expand...

My opinion on this has always been it has to do with the direction of coolant flow. Coolant flows from the front to back first. The back is often running hotter. Toyota inline engines generally seem to fail back cylinder first; I've seen it time and again on both gasoline and diesel 4 and 6 cylinder engines. The conclusion that many have made is the failures are related to coolant flow.

1HZ doesn't have problems because it's not turbo charged. Throw a turbo on there and I place my bets on the DI engine (1HDT) not the IDI. DI wins everytime all other items equal. IDI's by nature of design simply absorb too much heat via the pre-cups. (This in my opinion is why the 2LTE and 1KZTE fail often - they are Toyota's only IDI turbo diesel's).

Coolant flow diagram for 1HDT:
1hdt_coolant.webp
 
someone must want to crank out some performance with that upgraded pump.... cough speak up someone.
The plenum design does suck on the 1hz/1hd-t. I think enlarging it would help dramatically.
Get more air in is always a good plan.

Make sure your injection system is up to snuff. I have heard of leaking nozzles causing pistons to crack or even melt.
This is something I am beginning to think that the 1hz cracking pistons on turbo'd 1hz trucks.
With having the fuel turned up and old/weak injectors having more flow pumped through them.
The dripping diesel can be concentrated onto one spot on the piston. Over time burning through or stress fracturing it.
 
Yea the cooling system is definitely an issue as well. Tapping in a dual coolant feed somehow would probably work wonders.

As for the pump above, the goal is about 290-300hp available fuel with the option to down tune to individual preference based on boost control.
Bits are taken from various different platforms; Cummins, Yanmar, Denso, Volkswagen,
All thrown in for the very best of everything.
In my building experience, Denso pumps are a bit more refined in setup, but the quality of parts is somewhat lesser than their German counterparts. Thus the reasoning behind the mix of parts.
 
good to hear, thought you might be the goods. ya the plenium retrictions is the main thing that got me going just a bigger reserve., im surprized nobody hasn't tuned lengthend the runners ,let alone the log exhaust.
 
something like this, but with 6 holes. VW aftermarket has it figured.... just as an example. This design supposedly flows enough for over 250hp on a TDI, which incidentally has less flow to cyl 1 and 4 in stock config. I know this has been discussed before, but the design is so simple, couldnt resist.
intake.webp
 
Just put a G Turbo Grunter Extreme on it, with the waste gate shut it will blow out to 28psi, air flow makes a massive difference. Snorkel - air box - G Turbo - ported head - 3" short exhaust.
 
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