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Practical Diesel Tuning: Larger Injectors and Fuel Pumps

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Larger Injectors and Fuel Pumps


00:00 - In most instances, the stock injectors and fuel pump will be sufficiently large to handle the fuel requirements of a stock engine running a stock turbocharger.
00:07 This of course isn't always the case but provided you're dealing with an engine that's popular for modification and tuning, shouldn't be too difficult to research and find out what the shortcomings are, and you'll need to address those.
00:18 Once you start getting serious about engine performance however, it's likely you'll need to address the fuel components and replace them with something bigger.
00:26 You options here will be very much driven by the particular engine you're dealing with and in some cases you'll have plenty of choices while in others you may struggle to find suitable upgrades.
00:35 Unlike the gasoline tuning world where port fuel injectors are rated in terms of their flow and cc per minute or pounds per hour, aftermarket high flow diesel injectors are rated as a percentage increase over stock.
00:46 For example, you may be able to purchase 30%, 60% or 100% larger than stock injectors for a common rail diesel engine.
00:54 When you're faced with the decision on purchasing new injectors, it might seem that bigger is better however I want to caution you there, that's not always the case.
01:03 Large injectors can provide more fuel flow for a given pulse width however, they can be difficult to accurately meter the smaller fuel quantities needed for idle and cruise.
01:12 Going too large with your injector size therefore can negatively affect idle quality as well as general drivability in the vehicle.
01:19 In particular, you may find the engine may become slightly noisier, exhibiting characteristic diesel knock, as well as producing extra smoke at cruise and idle.
01:28 In general, injectors in the region of 30 - 50% oversize can be tuned to still providing good idle quality and drivability.
01:36 However once you start getting into larger injector sizes, these really are suited more for competition use and some drawbacks should be expected.
01:44 Of course, when you're fitting larger injectors, then you'll almost certainly need to fit a larger fuel pump to keep up.
01:50 Just like the injectors, for the popular diesel engines, there's a wide range of fuel pump options to suit your requirements.
01:56 Since a lot of diesel engines aren't fitted with a lift pump and instead rely on the high pressure pump drawing fuel forward from the tank, fitting a larger high pressure pump can actually be problematic.
02:07 This is because the new high pressure pump may be able to support additional fuel flow.
02:11 However if it can't draw fuel from the tank then it can't do its job.