Solving 3 Problems With 1 Turbo - Fixing Turbo Smoke, Lag and Threshold with a Ball Bearing Turbo

Video Description

Turbo dictionary: https://www.youtube.com/watch?v=MTdIB4-PmyA&t=1555s The Turbo from the video: https://www.maxpeedingrods.com/product/t25-gt25-gt28-gt2871-350hp-gt2860-dual-ball-bearing-turbo-universal-for-15-20l.html?search=gt2871 Support the channel by shopping through this link: https://amzn.to/4fatbMb Patreon: https://www.patreon.com/d4a Become a member: https://www.youtube.com/@d4a/join I'm back in the garage! I'm not staying long but I decided to try and improve #projectunderdog while I'm there. The car that basically built this channel. My 1987 Toyota MR2 mk1. It will soon be 12 years that I own this car and during those 12 years I have done pretty much everything you can do to a car. I built three different engines for, two transmissions and I did a full overhaul of the suspension, the brakes, installed and wired a standalone ecu from scratch, installed water-methanol injection and so on and so forth. In it's current from the mr2 has a 4afe toyota engine from a toyota carina. This underdog economy engine has been built and boosted to around 300 horsepower. And while the car is extremely fun and a very special driving experience it still has 3 issues that I want to address and in this video I will try to solve all three of those problems with a single turbo. My 3 problems are: Turbo smoke, a high boost threshold and boost lag. To be honest the lag isn't all that noticeable but it's cooler to solve three problems with 1 thing than two problems. The turbo smoking is definitely the biggest problem as it's embarrassing and smells horrible. It occurs because my turbo is mounted very low in relation to the engine which means that the oil return (drain line) isn't vertical enough making oil draining back into the crankcase more difficult. The second issue is that my engine is in its original form an economy naturally aspirated engine and as such it only has a single pcv outlet on top of the valve cover. When you add boost, pressure in the combustion chamber dramatically increases and this inevitably raises the pressure in the crankcase too. Higher crankcase pressure means that it's harder for the oil to go back into the crankcase. All this means that the pressure balance around the piston-ring like turbo seals is upset. My turbo most often smokes when going downhill. As I go downhill, RPMs of course increase, and the higher the RPM, the faster the crankshaft. And thus the oil pump uh is also spinning. And the faster they spin, the higher the oil pressure and oil flow through the engine and the turbocharger. But when I release the throttle, the amount of exhaust gas going through the turbo rapidly decreases while RPM still remains high. That means that we have high pressure on the oil side of the seal and reduced pressure on the exhaust side of the seal. If the pressure difference is high enough, oil will leak past the seal and into the exhaust stream where it gets atmoized and burned by the hot exhaust gas creating a horrible smelling smoke. Turbo smoke can be resolved with a scavenging pump or an improvement of the crankcase ventilation. It can also be resolved with a dry sump system. However I will try to resolve it with a ball bearing turbo as a ball bearing turbo is designed to work with an oil restrictor. This means less oil coming in which should also mean less oil coming out and less oil means the oil shouldn't accumulate and build up and so the turbo shouldn't smoke. My other two problems come from the fact that I have a small 1.6 L engine with a relatively large turbo. And as such, I have a high boost threshold and the presence of boost lag. Boost threshold is the rpm at which your turbo starts to produce significant boost. For the sake of the example I will say that significant boost is 7.5 psi or 0.5 bar. Your boost lag is the time delay in boost generation that occurs after you get back on full throttle from a close throttle, while you're above the boost threshold. Boost threshold is measured in rpm and boost lag is measured in time. In this video I also do logs with a journal bearing turbo and a ball bearing turbo and compare them in detail so that you can see in practice how this data looks on a real car and engine and how a ball bearing turbo impacts boost lag and boost threshold. A special thank you to my patrons: Daniel Zwoa Meda Beda valqk Toma Marini Cole Philips Allan Mackay RePeteAndMe Sam Lutfi Cakeskull #d4a #projectunderdog #boostschool