This is not a delay inherent to being computer controlled or drive by wire, computer controls are capable of being instantaneous. These driveability issues are forced on people by the EPA. Before the ridiculous delays with drive by wire it was absurd engine behavior when letting off the throttle either slightly or entirely. EFI engines seem to leave the IAC open to slowly come down to idle, and annoyingly when letting off the throttle to change gears the RPM actually increases. Compare that to a carbureted engine which has clean crisp immediate throttle response, or a mechanical diesel which does exactly what you tell it to and nothing more or less. The major driveability issues with EFI were a showstopper for me, let alone to added cost, complexity, and reliability issues. No EFI for me.
idi vs psd question
- Thread starter ericwade381
- Start date
This is not a delay inherent to being computer controlled or drive by wire, computer controls are capable of being instantaneous. These driveability issues are forced on people by the EPA. Before the ridiculous delays with drive by wire it was absurd engine behavior when letting off the throttle either slightly or entirely. EFI engines seem to leave the IAC open to slowly come down to idle, and annoyingly when letting off the throttle to change gears the RPM actually increases. Compare that to a carbureted engine which has clean crisp immediate throttle response, or a mechanical diesel which does exactly what you tell it to and nothing more or less. The major driveability issues with EFI were a showstopper for me, let alone to added cost, complexity, and reliability issues. No EFI for me.
i still prefer MFI.
i cannot wait to get my hillborn set up done!
far superior to a carb for track apps
needs alot of other stuff for a gasser to run on the street tho.
i cannot wait to get my hillborn set up done!
far superior to a carb for track apps
needs alot of other stuff for a gasser to run on the street tho.
Saskredneck
Full Access Member
My 6.9's would beat my 6.0 powerstroke off the line but probably wouldn't get much more than a truck length on the 6.0 before the turbo spools and it's at 90mph before the 6.9 hits 45 mph. I could pull almost two truck lengths from a stop against my buddy's 95 7.3 with my N/A 6.9 then the psd would catch up and pass, 7.3 powerstrokes are dogs compared to the 6.0/6.4/6.7 but like the Idi's will run forever.
ericwade381
Full Access Member
So I have to ask doing landscaping how are the idis at say stump pulling for shrubs with that snappy response?
When I bought my truck I was redoing the front landscape at our old house. I had been tugging with a Dodge Grand Caravan (with a hitch) to get some of the plants out. What a pain.
I got the truck, hooked to the biggest bush in the yard, dropped into 1st and let out the clutch. It just went forward with no resistance. I thought that the rope slipped off the hitch.
Nope, it just pulled the whole thing out of the ground!!! 
I would say they work great!!!
I have several landscaping customers with IDI powered trucks and they love them for their affordability and durability. I've come to have great respect for the 7.3L PSD since owning one, but they still have a few Achilles heels which will leave you wishing you had an IDI. Injector cups most notably. As you move forward from there to the 6.0L and later models, they all ratchet up the screamin' demon' kind of philosophy. Where as the engine really has to turn a lot of R's to develop the power that it does. I prefer the older technologies where the torque curves were lower, and less RPM's means longer life. There are some very strong running IDI's out there, that put out plenty more HP and torque than stock PSD's did, but as was said, once you get to modding the modern engines, they can outperform in every direction except in your wallet.
derjackistweg
Full Access Member
This discussion is basically between a N/A and a Turbo engine.
A Turbo engine makes ONLY power when you have enough exhaust speed, as this spools the turbo (except the new audi with electric powered turbo). Exhaust speed is generated from rpm.
Therefore a slightly less powerful N/A can be felt more powerful than a turbo in very low rpm. But obviously only BEFORE the turbo kicks in.
VGT turbos (variable geometry) are a HUGE benefit: the smaller the inlet house of the turbo - the faster the turbo kicks in, due to a less amount of exhaust speed needed in a "smaller turbo". With higher rpm the vanes "open" the turbo house to full volume and so the whole bunch of the turbo is available.
Great deal for every turbo.
In 2 words: turbo lack.
A Turbo engine makes ONLY power when you have enough exhaust speed, as this spools the turbo (except the new audi with electric powered turbo). Exhaust speed is generated from rpm.
Therefore a slightly less powerful N/A can be felt more powerful than a turbo in very low rpm. But obviously only BEFORE the turbo kicks in.
VGT turbos (variable geometry) are a HUGE benefit: the smaller the inlet house of the turbo - the faster the turbo kicks in, due to a less amount of exhaust speed needed in a "smaller turbo". With higher rpm the vanes "open" the turbo house to full volume and so the whole bunch of the turbo is available.
Great deal for every turbo.
In 2 words: turbo lack.
82F100SWB
Full Access Member
A 7.3 with a chip can have response just like a 6.9, stock programming will not allow so much as a hint of smoke, and gives very little timing advance at low rpm and off of boost. Both of these make the engine seem to be very turbo dependent. However, the IDI's higher compression will always make it seem crisper.
david85
Full Access Member
I'm a little surprised it took so long for someone to point this out.
A 6.9 has 22.5:1 compression ratio. Nobody builds a DI diesel with that kind of CR these days and certainly not for an EPA regulated light duty truck. So yes, they engine management system does have to wait for the turbo to spool. It has nothing to do with any perceived weakness of the electronic control system. Once the turbo spools, the dynamic CR gets high enough and the rest of the fuel is unleashed. Once that happens, IDI is left behind. Peak for peak, yes, the direct injected PSD will generate higher numbers. However off the line, a PSD will not easily match the low end torque of an IDI unless copious amounts of smoke are involved.
I drive a 2010 duramax for work these days and its the same with that one. Sluggish off the line but low end torque is quite good once rolling.
derjackistweg
Full Access Member
Sorry guys but commission ratio has nothing to do with this topic!
A diesel engine fires automatically the injected fuel at a point of heat. No spark obviously.
To do so Rudolf Diesel invented the pre combustion chamber. This kind of diesel engine works ONLY at a certain point of compression. Roughly 21:1
A direct injected diesel engine fires directly into the cylinder and due to that the compression NEEDS to be at roughly 17:1.
There is no way to let an DI diesel work at 21:1 or the other way around! This is just physics. In a Otto engine this is different.
A 6.9/7.3 is indirect injected.
7.3/6.0/6.4 etc are direct injected.
This all has actually nothing to do with low torque, emission standards. But obviously modern standards help to reduce emissions.
david85
Full Access Member
If by "commission ratio", you mean compression ratio, I disagree that it has nothing to do with it.
Those 17:1 static compression DI diesels have a dynamic compression ratio similar that of the non turbo IDIs once the turbo spools up. Once you start modding with more boost, the dynamic CR goes higher still.
