bigport TVIS mod to all 8 ports.

[altezzaclub]

Well, the Girls KE70 has had the 4AGE for 5 or 6 years now, and more recently a Haltech running it. Behind that is the lightest flywheel I've ever seen, and a pair of Wade 267deg cams, extractors and a 2" exhaust, all on the stock inlet system... It has always been a dog low down, even with a stock ECU it couldn't hold an idle, and the last mods were Banjo making me a Hall Effect sensor setup for the distributor and a set of COPs.

Then it died earlier this year and I found enough carbon under the valves to drop the compression at cranking speed, and the TVIS plates heavily carboned up.

Having made some movies under the inlet system with an iphone I realised the Haltech told the TVIS to open up or close but in the wrong language! They had been open all the time!

I found an output in the Haltech that worked like I wanted, but opening them was nothing great.. I could move the opening of the TVIS throttles anywhere in the rev range and nothing made a big difference. The 4 ports usually open can do what the motor needs.

So I figured I'd get rid of them and run 8 throttle plates against the head and no throttle body, using the stock 8-runner inlet.

First up was a look at Garage4AGE and his dyno runs. All the power increase is before 60% throttle, then you get diminishing returns.

Then an excellent tuning page I came across, giving the max power per throttle body size.

https://engineeredbydesign.co.uk/Pages/Calculators/ThrottleBody.php

Stock is four 30mm runners in the TVIS system, with 4 closed. That is good for 220KW at 7500rpm

Open the other 4 TVIS 30mm runners and its good for 440KW!!

The stock 55mm throttle body can power the 220KW that takes 4 TVIS runners, although 60mm would be better. Which brings up a interesting question, does one throttle body of a certain area flow as much as 4 ITBs adding up to the same area?? Each ITB flows once in 4 strokes, then it flows nothing for the rest of the time. A single throttle body flows its max all the time, just dividing that air flow from one cylinder to the next. So in theory I think the 4 ITBs should be smaller than a big single.. Anyone know about this?

OK, meanwhile, everything is waay too big for what I want. I put in a 1600cc V8 to get figures for 8 runners working, one for each valve.  To get 125KW at 7500rpm needs eight 14.5mm runners!!

Far too small to even engineer, so I worked on 20mm. In theory that is good for 200KW, matching the stock throttle body, and not many slightly modified 4AGEs are going to worry about more than that.  These are 20mm coins in the 30mm holes of the TVIS gasket.

So while Josh was away for the ARC round in Tassie I bought a 33mm round bar of alloy and got on the lathe. I made them 30mm long so they stick into the head close to the injector, stepping them from 30mm OD down to 25mm OD as the port reduces in the head.

Then I put the inlet system back on. Did you know you can remove the stock inlet system and leave everything else like the injector rail on? Toyota were very neat with this design.

Instantly the motor idles now, from cold even! Pulls up the driveway without lots of on-off-on throttle trying to work the revs up, and cruises easily around town at 50kph. I have nice long hill just of of town that I time 60-100kph in 3rd from a particular roadside sign, and its gone from 12.23sec to 11.8sec. That's 3000-5000rpm, the most useful range for daily driving.

I haven't found any loss up to 6000rpm, I don't need more than that, and everything below is better. I've been changing the Haltech fuel cells all week as it suddenly ran lean, more air getting into each cylinder. I'm dying to see the fuel usage after a tank full.

I can put the original TVIS throttles back in, or I can drill right through the lot, mount tiny 20mm throttle plates, put a cable in the middle where the TVIS actuator is and a TPS on the back by the firewall. Then it needs a vac system for the brake booster or unboosted brakes. Then you get instant throttle response.

I'll see how enthusiastic I am in 6months!

 

 

 

Edited 2 hours ago by altezzaclub