Quote:
Originally Posted by boostednut
The common thread in all the builds I've seen so far (well the majority of them) is to upgrade to both the lt4 pump and injectors.
However I also know off previous cars I've built, that when a platform is still relatively new (even the earliest of c7's especially considering the popularity of port vs direct), things haven't usually been fully investigated. And as time goes on, limits (in terms of strength, durability etc) become more concrete/understood. This can be a pretty big factor in cost to build.
Has any shop/any individuals explored which one is actually the limit? I've seen at least a post or two suggesting that the lt1 injectors really aren't the issue, but the pump is. It would make sense that the pump is solely the limit, as an increased fuel lobe will take the fuel system noticeably further. (Low pressure issues assuming to be fixed).
Any comments, thoughts?
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In our experience the High pressure pump is the first Limiter and and a very hard limit that is unaffected by low side pressure unless low side pressure drops to around 30 psi then its range is limited even further.
I have run both 400 Kpa and 500Kpa low side pressure and the hard limit of fuel delivery was unaffected.
The reason is because the high side pump is a positive displacement piston pump and fuel is not compressible.
The LT-1 pump runs at 2175 psi and the LT-4 pump runs at 2901 psi, this will extend the range of the injectors but you will find the limit.
The big bore pump takes it to the next level.
You find that limit of the injectors by logging the High pressure pump and injector opening time.
When you exceed 6 milliseconds start looking for larger injectors.
Hope this helps.