Toyota/Lexus V8's
Discussion
Say it as it is why don't you 
Thanks for the heads up. Am I right in thinking two smaller units will spool up quicker than one larger one, hence less turbo lag? Albeit with other mods, I'm looking to atleast double the stock output of the engine, hence a fairly sizable turbo will be needed.
I guess I need to go back and dust of my thermo lecture notes from uni to put some metrics behind all of this.
Regards
Iain
Thanks for the heads up. Am I right in thinking two smaller units will spool up quicker than one larger one, hence less turbo lag? Albeit with other mods, I'm looking to atleast double the stock output of the engine, hence a fairly sizable turbo will be needed. I guess I need to go back and dust of my thermo lecture notes from uni to put some metrics behind all of this.
Regards
Iain
kirsty5150 said:
Could be a bit of a pig to sort the exhaust in a "nice" way. Two turbos are easier to package, and should spool up a bit quicker.
Ive built twin turbo systems in the past. They are defintaly not easy to package. In reality, its twice the work, and complicates intercooler plumbing.
In some ways, yes, the exhaust system side of things may be nicer, and potentially easier to make it more efficient.
But overall, a twin will usually be harder to build.
With hindsight, if I was to do such a thing again, I would defo opt for a big single, unless space restrictions within the car really did force a twin install.
As for the twins spooling faster. With todays modern turbochargers, the differences will be very small. Its an old excuse, based on old turbo technology.
I've been doing all the research and the digging and the ideal system for my purposes ( 400bhp with Lexus reliability) seems to be a twin turbo set up running with a GT25 or even better GT 28 fed off a simple log style manifold on each bank of cylinders. These turbo's will feed air into a simple intercooler with two inlets, one at each side, at the base of the intercooler with a single exit coming from the interecooler high up on the offside and feeding the inlet manifold through standard throttle body. The standard ECU will be controlling the spark and fuelling when pottering around off-boost, but when on-boost either a piggyback computer running from a boost sensor will provide extra fuel through a couple of extra injectors in the injection plenum, or I may initially try a set of bigger injectors and a rising rate fuel regulator for simplicity.
The engine is well protected by knock sensors and as I won't be going too mad initially the intercooling, standard knock protection and extra fuelling should handle the moderate amount of boost required to get to my initial goals.
This is all being shoehorned into a Cobra ( one of two Lexus engined Cobra's presently being built in my garage), so once I've saved up for the Turbo's etc I'll be giving it a go. Anyone know of a brace of GT28's going cheap?
Cheers,
Tony
The engine is well protected by knock sensors and as I won't be going too mad initially the intercooling, standard knock protection and extra fuelling should handle the moderate amount of boost required to get to my initial goals.
This is all being shoehorned into a Cobra ( one of two Lexus engined Cobra's presently being built in my garage), so once I've saved up for the Turbo's etc I'll be giving it a go. Anyone know of a brace of GT28's going cheap?
Cheers,
Tony
Stick a wanted on post on www.driftworks.com on the forum for your T28's & also get on the www.toymods.org forum for all the info you'll ever need.
Tony427 said:
...piggyback... rising rate...
You're sure trying to make things hard for yourself
If turbocharging you'll find it much easier, quicker, safer and more reliable to use a new ECU to control the engine, piggyback ECU's, rising rate regulators that raise the fuel pressure etc, they can be made to work and I'm sure some people swear by them, but most people swear at them when they take a head off and look at their melted pistons. You really can't go far wrong with something like an Emerald - you can even get it mapped by Dave Walker for £250 extra once it runs. Wiring is easy, all the sensors are already there or if they need changing, you already have a hole/mountng point for a new one. The new K3 ECU even has specific functionality for turbo engines. (Could just as easily use DTA/MBE/etc)
chassis s3 said:
Just found this company www.camshaftshop.com/camshafts/vie that do alsorts of variations. Not pocket money though.
Woot! That is very useful to know, thanks. Not pocket money as you say, though with $ rate as it is that's what I'd expect for a four cam set. After all, a cam kit for a DOHC four pot is about £250.
busa_rush said:
Tony427 said:
...piggyback... rising rate...
You're sure trying to make things hard for yourself
If turbocharging you'll find it much easier, quicker, safer and more reliable to use a new ECU to control the engine, piggyback ECU's, rising rate regulators that raise the fuel pressure etc, they can be made to work and I'm sure some people swear by them, but most people swear at them when they take a head off and look at their melted pistons. You really can't go far wrong with something like an Emerald - you can even get it mapped by Dave Walker for £250 extra once it runs. Wiring is easy, all the sensors are already there or if they need changing, you already have a hole/mountng point for a new one. The new K3 ECU even has specific functionality for turbo engines. (Could just as easily use DTA/MBE/etc)
I'm using the standard auto box which is controlled by the standard ecu, changing the standard ecu to an aftermarket one will require another ecu to run the gearbox. The standard auto box is good for 450 bhp and a play with the springs in the valve bodies in the gearbox will firm up the gearchanges nicely. For less than £150 I can even get a Tiptronic gearbox adaptation kit for the standard box from Australia.
So the plan is to use existing engine management system, ably assisted by a simple piggyback arrangement to get me to 400 bhp, using the standard box, then when or if I get used to the power and want more, I can go for a lowered compression engine, make full use of the turbos' capabilities, use a Megasquirt ecu system and convert the car to a manual gearbox.
I ran a 330bhp BMW V8 with 5 speed Tiptronic in my last Cobra and that was scarily fast on occasion, so I think 400 bhp will serve my needs adequately for some time.
Cheers,
Tony
stevieturbo said:
Any details on the tiptronic thing for the gearbox ?
A friend bought an early LS400 recently....
A friend bought an early LS400 recently....
Go to www.lextreme.com, click on the V8 section and do a search for Tiptronic conversions. A member of the site makes the kits up a few at a time.
Cheers,
Tony
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