Snowman3645

I was just reading about a guy who want to put an overly large turbo on his y8 and was asking how to make a dent in his lag problem.
I started thinking.... These are some questions I came up with:

Could you set VTEC to start at something like 1000rpm and turn off once the boost picked up? I know that would be terrible for a daily driver and probably a nightmare to tune.... But it looks pretty in my head. Haha

What kind of difference in spool time would you see between a stock head and a larger cam if everything else was the same?

And could NO2 be used in the same fassion?

Second:
I heard putting a 2002 si crank in a y8 fits and will lengthen the stroke. Confirmation please?
If so how would it hold up to a turbo at something like 12-15lbs?

Flamers welcome, shoot me down if you see fit. But if anyone has tried it.....

Turbo-LS

iTrader: (4)

You arent building enough oil pressure to engauge vtec that low and it will definatly hurt performance. I fyou turn vtec on to low you dont have enough swirl in the combustion chambers and the car will be a dog more than usual. Different cam will help. NOS will definatly help if its built for it. Just sound slike he wants to put a huge turbo on there for the hell of it but if its for real it can be done and be quick. someone ran 9's in a single cam d series with alot of work and a very light car.

Just put a properly sized turbo on there. its not going to make alot of power liek a b series without crazy work to it and at that point why bother

Tony the Tiger

Turning on VTEC earlier doesn't help... The high cam will only benefit if the engine is building enough air velocity to make use of the VTEC cam.

You will see a pattern... Cars with small turbos want early VTEC.. Once boost builds, the engine's airflow characteristics changes. Such examples would be a JRSC Honda that benefits with VTEC being at a low 3000RPM.

On a laggy turbo car, your VTEC will be based on how soon the turbo builds boost, or naturally the torque starts to drop when the car is still lagging. By installing a set of turbo cams, it will marginally help the lag, but improve mostly when the turbo is beginning to build some positive pressure.

Stroking the motor would help the lag... You will lose out on the redline though.

You can also install a shorter final drive for shorter gear ratios. It will let the car pick up sooner and feel less laggy, but it doesn't improve RPM vs lag however.


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This kind of question will get you shot in a heartbeat... You've failed to mention the MOST basic things in that question... What cam and what turbo? Useless question.

TurboK

A devided turbo manifold will do you alot of good where lag is concerned.

Snowman3645

Alright then, to avoid a gun fight I will elaborate.
Here is my hypothetical set-up:

Vitara's
H-beams
FMIC with 2.5inch plumbing all around
Hondata s300
Turbo: hx35 or similar truck turbo
From a junked deisel.

Basically I would like to get opinions on what upgrades are going to work the best together to get this oversized turbo to spool before christmas 2009 on a y8. I am a student so I don't have 5k but I can save up. Say my power goal was in the relm of 300-399whp
I have not yet decided on the following:
Head configuration-
Intake mani-
Exhaust mani-
Injectors/fuel system-

I know a few people I could get dsm set ups from for cheap but is that gonna last me at that level?

mr1320

2steps also help.

beepy

For your power goals that turbo is far too large. just do the proper engineering. Choose a turbo that is most efficient in the range you are going to use it at! Worrying about turbo lag is pointless unless you NEED the airflow that a larger, laggier turbo can support. Compressor maps FTW. You will find that a TD05 turbo has more than enough capacity to support 300 horsepower, although you will need a small, efficient turbine trim to match the 1.6l displacement.

As for the initial question: There are two tried and true ways to remove lag. One, anti-lag: Injecting additional fuel (or propane) into the exhaust pre-turbo to increase the exhaust pressure. Great for drift cars. Bad for turbos. Two: Nitrous Oxide. A small shot of NAWS at low RPM will produce a great deal of exhaust flow. As nitrous decomposes it produces 33% O2 and 67% N2. Combine that with the fuel to support, and you can be jamming 50-100% more gas through the exhaust valves.

extralargenog

iTrader: (1)

Thats not entirely true... I saw a noticable difference openning VTEC at 3500ish.... It DEFINATELY helped spool, not by a magniutude of OH MY GAWDz VTak is kickin in yo" BUt on the dyno it showed a notable improvement. Se the engagement tober dependant on load so when cruising on the freeway it wouldnt be in vtak unneccessarily too.. WOrked out good for me...


Ill try to dig up the dyno.

here: If you llok you can SEE where it made a difference at 3500 where it engaged (I aolmost typed cracked yo!!! LMAO). Unfortunately I couldnt dig up a printout without the vtex crossover that low, but it DEFINATELY made a difference.





OH... Here vs 4750:




:O)

rmcdaniels

I put a little supercharger on mine to help spool the turbo. It made a big difference. I lost some HP up top, but gained a lot down low and the turbo spooled almost instantly from anywhere. Below 5000 RPM the supercharger made a huge difference in turbo response and power, while above 5000 RPM the turbo was better off by itself. For drag racing I'd just go with the turbo, but for daily driving, road course, or autox, the dual setup was much nicer:

TheShodan

iTrader: (14)

Not necessarily. The engine makeup is more important than simply having a divided manifold and housing. There are MANY more factors involved.

Snowman3645

Some good replies thanks guys

Wow I have never heard of a SC and turbo together wouldn't it hold up the turbo? Unless they could run the same CFM? I guess that's why you lost on top.

I am actually really interested, I want to get an eg hatch to put my motor in once I'm done building it and road race. Which is why I was asking about spool times, the deisel turbo was more of a conversation starter.

But keep it coming!

I'm lovin all the input

rmcdaniels

The SC was bypassed after it spooled the turbo:

https://honda-tech.com/forums/forced-induction-16/dual-sequential-chargers-1293497/

For road racing, just build a good motor and learn to drive. I've seen guys build setups with turbos making low boost and they are very linear. I like those setups, but in an EG hatch 200 WHP is enough to win and you can do that NA with pistons/rods, plus it will last. I won both of my last two road-racing events with around 180 WHP in an EG hatch, and one event was on street tires. I'm putting together a new SC-only setup, but I may ditch it all and go with a NA K24. More power is nice for road racing, but there's so many other things to worry about that you're better off with something simple and rock-solid so you can concentrate on driving.

TheShodan

iTrader: (14)

^^Amen to that. Even more to worry about with Turbo AND road race like I have for years.

Tony the Tiger

VTEC is basically just giving you more overlap and lift at a certain RPM. On the dyno, you are loading the engine from a really low RPM and there is enough time for your engine to deliver enough airflow and load onto the motor. That is why VTEC is based on RPM and throttle, and in some cases, based on MAP load as well. Once you take your car on the streets and dead stab your throttle from 3000RPM at say 2nd or 3rd gear, you will notice you will actually increase more lag.

The second reason of your power gain is that your car could already be building plenty of positive pressure. Your dyno shows a gain at 5500-6000RPM, but your VTEC engagement was changed at a much lower RPM. This again, brings up to what I mentioned above from the engine being loaded at a low RPM on the dyno. Once there is enough "load" on the motor at the dyno, the slow steady dyno pull allows the big turbo to build some positive pressure and therefore, make use of a larger cam profile, as mentioned on my earlier post :

Tony the Tiger

There is always a huge misconception about turbo "lag"... Most people would comment lag as when the turbo builds boost based on RPM .

I'd sum it up that there are usually two types of lag, one is how long it takes the engine/turbo to build maximum torque based on RPM, and the other is how long it takes after you go WOT... This becomes more of a response lag which most roadracers are mostly concerned with.

There is a lot of playroom between lag vs RPM and lag vs throttle..

A small GT28 turbo with a small hotside will deliver big torque at a low RPM, but it may not necessarily mean it will build instant torque when your RPM's are hanging at 6000+ RPM and going WOT versus a larger turbo simulating a corner exit on a roadcourse. This small GT28 for example, may take 22 PSI to make 380 WHP. Smaller is not always better.

A GT30R for example, is a very snappy turbo with really good response up at higher RPM's. Because this larger turbo can make a lot more power at a lower PSI, it can already match the power/torque output of a smaller GT28 at 6000RPM at a much lower 14 PSI for example. The key is knowing whether the GT28 turbo or the GT30R turbo would build power sooner... Would it be a GT28 winding up to 22 PSI at 6000RPM, or a GT30R quickly spooling to 14 PSI at 6000RPM? All this would be measured with an engine decelerating at 6000RPM (off the throttle), and then quickly going back on it.

Most likely, you will notice that the larger GT30R turbo will build power and torque faster once you mash the throttle at a high RPM.

I persronally like turbos that would react instantly if I am at a higher RPM. It gets close to an NA motor when you want an instant throttle/engine response once the RPM's are above a certain level. Just like all roadracing, you don't race a car below a certain RPM, and the turbo car should behave like an all motor car. I don't care much about RPM vs lag because good gearing and a higher redline can always make up for it, but as long as it is not excessive lag (ie: turbo spools at 6500RPM).

tony413

nice sum up.

extralargenog

iTrader: (1)

The only change made was the crossover, you can hypethetically find 1000000 reasons it made a difference, although minimal, All I said is that it DID make a difference. It did. The sheet shows it. What, the car doesnt get loaded on the street???


I DO understand what youre saying.. valid point, yet the sheet doesnt lie. Opening it earlier spolled the turbo a touch eralier... ANd made more power. Period.

Come on man.

TheShodan

iTrader: (14)

Tony, you know.. just when I think I can say something that is very eloquent, you go and do a better job, bottom line. My hat is off to you.