Everything You Can Do To Improve Lag

[R_34]

Didn't measure it as I sent the turbine housing to be coated directly when I received the turbo.

So I don't have a before/after.

I'm pretty happy of the coating on the turbo, so as soon as I have tu pull the engine for wathever reason I'll send the standard manifold too.

The effect will not be gigantic though, but I will use what I can to reduce lag and lower the boost threshold as well as reducing heat leakage in the engine bay.

Don't expect much more than 200/300 rpm improvement, especially on standard short runners manifold. The effect should be more noticeable on aftermarket manifold.

[Piggaz]

Can you be more specific?

I don't think the standard cams would be a better option than the tomei type Bs, when aiming for 400-430kw awkw

If you're going to the effort of stroking it, you shouldn't be dicking around with fairy poncams anyway. Too much duration for the lift IMO.

[GTR_JOEY]

Didn't measure it as I sent the turbine housing to be coated directly when I received the turbo.

So I don't have a before/after.

I'm pretty happy of the coating on the turbo, so as soon as I have tu pull the engine for wathever reason I'll send the standard manifold too.

The effect will not be gigantic though, but I will use what I can to reduce lag and lower the boost threshold as well as reducing heat leakage in the engine bay.

Don't expect much more than 200/300 rpm improvement, especially on standard short runners manifold. The effect should be more noticeable on aftermarket manifold.

200/300 rpm reduction in lag from ceramic coating..though I wish it was true that Sounds unrealistic to me.. Anyone else got experiences with ceramic coating before and after?

Romain, did you notice a reduction in engine bay temps??

[GTR_JOEY]

Bigger is better remember Paul..

If you want response rip out those weak pon cams and get something more aggressive.. And no I don't mean bigger duration.

Don't put bigger valves in as it will not help your response,

Raise compression to 9.3-9.5

[discopotato03]

If you build an engine that makes acceptable torque down low mild turbo lag isn't as much of an issue so think engine first .

Mechanically speaking only three things increase an engines performance , capacity CR and revs . Forget revs ATM .

Capacity is in theory the easiest way because for the same state of tune ie cylinder temps and pressures because you have have a greater volume of charge to burn .

CR helps because you compress the charge volume more increasing its density .

Go back to 1988/89 and look at how Nissan went about making power with RB26s . Lowish CR with big intercooler (for the day) and big lungs in multiple throttles - good throttle response here .

Turbos were on short three branch manifolds so short path to turbines and light ceramic turbines . Turbos had modest sized housings on them . Twin turbos with twin integral gates is effectively same as twin scroll single turbo with twin gates , but TS single manifolding won't be as good .

Two fold advantage with E85 , better evaporative charge cooling and chemically less detonation prone . This allows you to use a high static CR and suitable pistons can have better quench so even greater detonation resistance .

Cams , generally short timed big lift cams are good in engines that need torque early on . They work because big lifts open valves further to fill the cylinders but the limited off seat time means you keep/maintain good trapping efficiencies . This means you don't charge the cylinders and lose part of what you got by it leaking out either valve because of extended durations . Long duration cams are great at high revs because the engine events are happening so fast that the gasses don't get enough time to leak back either way .

Shorter duration cams have less overlap timing because the emphasis in on getting best scavenging at less than telephone number revs .

Turbos , if there is a modern update to what you have performance wise now I'd look that way with twins on a std capacity RB26 . I'd look at the maps of your turbos and see if there is say a GTX equivalent that has a more efficient compressor ie possibly GT2860R .

Valves , some people think big bore RBs like 25 and 26 didn't have an idea valve size ratio inlet to exhaust with the exhaust being slightly smaller . I don't know about RB26s but you can get slightly OS valves for RB25s and they go straight in with just a bit of seat work to the existing seats .

I think you can look at closing up the low down turbo engine torque hole two ways , better or smaller turbos vs better engine itself performance .

Raise the static CR better quench and cams with better trapping efficiency . These lead to higher cylinder pressures down low and that means more torque .

Smaller turbos tend to have smaller passages which increase gas speed in relation to engine speed , GTSSs are like this .

Sometimes same size as existing turbos but with lighter forged/milled compressors help because there's less inertia for the exhaust energy and turbines to accelerate . Better aero wheels can add a bit too .

Tuning/fueling . IMO the best injectors you can get your hands on should help down low for two reasons . Modern ones like EV14s have much lighter internals so they are faster acting and more accurate withy fuelling . Good spray patterns help too and you can't forget that accurate well atomised fueling can make a considerable difference to how much torque an engine makes at low speeds and light loads .

Also a tuner with the smarts meaning strategies to make the fueling and timing give the best everywhere .

My 2c cheers A .

[Dose Pipe Sutututu]

Convert to a VNT turbo, haven't seen anyone really use them on a RB26.. I know Stao from HyperGear has a few prototype ones going around on his RB25 test rig and it has produced marvellous results.

[hypergear]

Currently working on Electric assisted turbocharger prototype. It is currently getting the 490rwkws SS-5 turbocharger sitting on 3.2psi with car powered off. That is totally lag free.

[GTSBoy]

Currently working on Electric assisted turbocharger prototype. It is currently getting the 490rwkws SS-5 turbocharger sitting on 3.2psi with car powered off. That is totally lag free.

That will probably drop to no boost at all when the engine is running, but it is certainly better than not having the electric assist at all. I suppose the real question is, what speed does the elec motor run the turbo's shaft, and how much time does that buy you in terms of having to accelerate a shaft up to truly useful speed? Compared to having no assist at all that is. If you can quantify it in terms of seconds (or milliseconds I suppose, it may well end up being less than a second in some circumstances) then people can relate that to how much rpm advantage they would gain on an acceleration ramp up from off boost to on boost.

[hypergear]

Fist of all, Don't get too excited, this has a long way to go, and I'm just working on it with spare time as a Hobby.

The electric version generated 3.2psi of boost once engaged. How ever engine consumes more air as it revs. So boost level declines as engine RPM increases.

Still a very noticeable amount of gain compare to NA:

Reds are with Electric assisted only. Green is NA.

The electric motor can not be strapped onto the turbine shaft, it must be isolated when turbine shaft speed is greater.

Per Boost curve above, Ideally would be having electric motor to detached at 70.000 turbine shaft speed, and that is 3.2psi on this specific compressor.

This turbocharger the way it is, currently building 3.2psi at 2500RPMs. The Electric motor should add momentum to the turbine shaft, Once electrically assisted, we would have 3.3psi at 1000RPMs. So I'm expecting an difference of 1000~1500RPMs. in which we might see 490rwkws with 29psi reached by 3800RPMs.

[R_34]

Romain, did you notice a reduction in engine bay temps??

Again no before/after test. I had a CA18 with tubular manifold heat wrapped, a GT2560R with a blanket the viscous fan and the shroud before, and now the RB20 with oem exahust manifold, ceramic coated turbine housing, all the heatshield, the viscous fan is here but no shroud installed.

The engine bay is cooler now than with the CA.

I noticed that most of the heat is coming from the manifold rather than the turbine housing after the engine has been shut off.

Interesting thing the electric assisted turbocharger.

Which is the voltage of the electric engine and how many amps does it draw ?

[GD51LA]

Ok, sound like we getting somewhere

One thing at a time, first of all CR

How high can I go? I don't want the highest recommended, I'll go one step down

What is that 9:3?

[Ben C34]

One step down?

So if it happens to be for arguments sake 10.0 :1 is the highest (which it's not, there's no magic highest number, there are many different reasons for this) you will go 9.9 :1 ? Isn't that 1% less? What would that achieve?

[hypergear]

Interesting thing the electric assisted turbocharger.

Which is the voltage of the electric engine and how many amps does it draw ?

Its 12 volt and draws a maximum of 100Amps, so it would be similar to a Starter motor. It only comes in for about 2~3 secs a time. It will be a long time before I can come up with some thing working properly.

But VNT stuff do work. and do make a lot of differences.

eg:

Standard ATR45 (GT3582 equivalent) result based on:

R33 GTST, Factory spec engine, with high mount and external gate.

431rwkws @ 25psi E85 fuel, full boost reached at 4650RPMs

ATR43SS-4 Alpha. makes 435rwkws @ 25psi also, while making full boost by 4150RPMs, Nothing's changed except turbocharger:

[GD51LA]

I was referring to the earlier suggestion of 9-3 9-5

Would 9-5 be the higher end of a (turbo) application

How do we get 9-3 CR, I've only notice 9-1 pistons

Do I just custom order the 9-3 pistons? Do I just ask CP to make them up

Or do I get 9-1 pistons and achieve 9-3 CR in other ways, gasket/machining etc?

[scotty nm35]

I have turbo'd many high comp 10+ engines, they respond well on e85, but you need to drop the boost savagely on 98.

Critical is keeping the cylinder pressures under control.

[discopotato03]

The dynamic CR is the important one not the static (measured) CR . All else being equal an engine with long duration cams generally has a lower dynamic CR because the valves trapping efficiency is lower at lower revs . The less charge air you trap in the cylinders when all valves close the less you have to compress so the dynamic compression ratio is lower . This is why nice street turbo engines have short duration cams in them , higher lift versions allow better breathing but without the reduced dynamic CR caused by earlier opening and later closing valves . The only useful thing long period cams do is allow better cylinder charging at high revs but you lose in the low to mid range area .

The way to get back some of what you lose with long cams is to increase the static or measures CR , it works because the less air ingested is compressed into a smaller space so the dynamic compression pressure loss isn't as much .

Broadly speaking increasing the CR of an engine with not particularly responsive read big turbo/s will help the bottom end because of the above reasons . The thing is that FI increases cylinder pressures and temps too so when on boost the forced dynamic CR is the one to watch . High temperature is what generally finds the detonation threshold .

Other things like throttling contribute , ITBs generally have less restriction than singles and allow better cylinder filling in most circumstances .

The theory is the best filled cylinders make the most power (torque) provided detonation or thermal overload doesn't destroy things . And heat has to be able to escape easily at the end of the cycle .

A .

[Ben C34]

I would be extremely surprised if you could notice the difference of say 9.1 to 9.3 in an engine in terms of responsiveness.

Op, are you building this yourself or paying someone? If paying find someone good and trust them.

If building it yourself you can make it as simple or difficult as you like. People spend their whole life developing engines and still have things they want to try or learn. The basics are basic. Once you delve deeper it is never ending.

[scotty nm35]

An auto box with a well chosen converter will make lag non existent... For a price.

[juggernaut1]

Just throwing this out there .....extrude honing the turbo comp cover and ex hsg.....and stock ex manifolds if that is what you are using.

[scotty nm35]

Just throwing this out there .....extrude honing the turbo comp cover and ex hsg.....and stock ex manifolds if that is what you are using.

Will increase lag.

High gas speed is where is't at... 1 inch runners, 6 into 2 before the flange so there is no open areas for the gas to slow down. etc.