Turbo Upgrade

[jtmny1999]

I just got a NPR intercooler and 3'' piping that I want to install but I currently have Stock turbo that gives me alot of lag. I know that its just not going to work with a NPR and 3'' piping so I am looking for A hybrid T3/T4 with a internal wategate that will work with my set up. The problem is I am not sure what kind of trim to get and where to get it from. Anyone has this kind of set that can help me out. I'am runnig stock Fuel Injection System from 280zx turbo on my 71 240z. thanks

[pjo046]

Get James Thagard to hook you up with a proper turbo for your setup!!!

Not sure of the name of his website. Those who are, please chime in.

[jtmny1999]

Thanks, I will try to do a google search

[Scottie-GNZ]

That is the person to contact to spec and buy your hybrid turbo. However, the stock turbo should have no lag so you want to look into what is causing that. Best guess is that the engine is running too rich at low boost. Need to address that before you install a bigger turbo.

[Z-Gad]

http://www.speedshopthagard.com/

[jtmny1999]

I have a A/F guage it does run rich but after reaching 1500 and more boost It goes leaner. I was boosting 12 lbs without a problem it just doesn't boost as fast as other cars. When I did the swap I checked the shaft end-play and it did have a bit of play. It also leaks a bit into the intake pipes so I think its the turbo. I gotta say though when it hits 12 pounds it pulls be back on my seat. I just think that 3' pipes and a NPR intercooler will make it lag some more and sounds a little overkill.

thanks

[Afshin]

I will repeat what Scottie said, if you have excessive lag, it's likely NOT from the turbo. It is always best to fix any problem before going to the next step. Are the ignition related component all up to date? any exhaust manifold leaks, timing (too retarded will increase lag)...

T3/T4's are nice, but obviously will increase lag a little, but certainly not to much (depending on which unit) in a properly running set up.

Also 3" intercooler pipe is a little overkill, 2.5" is generally good for 400hp. So if you have not bought the pipes, I would advise you use a smaller diameter pipe.

You could also consider on of the garett GT ball bearing turbo's, supposed to have better design and less lag. Ask the turbo shop about them.

[EZ-E]

I would also have to suggest going to James Thagard, and dealing with him. My experience with hime was very pleasurable and he is very knowledgable. Always completely proffessional and willing to help in anyway that he possibly can.

 

Nothing but good things to say for Mr, Thagard.

[yo2001]

retarding the timing helps the spool up. I would check for the boost leak from the turbo to throttlebody or anywhere in between.

[frank280zx]

I will repeat what Scottie said' date=' if you have excessive lag, it's likely NOT from the turbo. It is always best to fix any problem before going to the next step. Are the ignition related component all up to date? any exhaust manifold leaks, timing (too retarded will increase lag)...

T3/T4's are nice, but obviously will increase lag a little, but certainly not to much (depending on which unit) in a properly running set up.

Also 3" intercooler pipe is a little overkill, 2.5" is generally good for 400hp. So if you have not bought the pipes, I would advise you use a smaller diameter pipe.

You could also consider on of the garett GT ball bearing turbo's, supposed to have better design and less lag. Ask the turbo shop about them.[/quote']

 

hmm well it depends on to what car he is comparing too, modern cars are loads less laggy, since the zx engine has virtually no compression, and a relativly large AR exhausthousing, i feel it is laggy aswel ( compared to newer Turbo's) a smaller AR might help, but would hurt flow, so you before you go that route, how much RPM do you want

[Clifton]

retarding the timing helps the spool up.

 

Don't think so, helps reduce knock though.

 

jtmny1999...

At what rpm are you seeing 12 psi by? 3k?, 4k?

[Afshin]

What Yo2001 is referring to is that with retarded ignition, exhaust temperatures go up which can enhance turbo spool up and at times reduce lag. However, that is certainly an overgeneralization and often not true, especially in the case of the l28et. Retarded timing can cause very low off boost power and sluggish engine response which not only will decrease power but also increase the time needed for the engine to built RPMs and therefore increase lag. The sluggish response and low off boost power also make the power build up very nonlinear, which makes the car feel very “laggyâ€.

So getting back to the topic of the post, retarded timing will decrease power, engine responsiveness, and increase the lag. Just set the timing at 18 then drive it and then try it at 22 and tell me which one builds power faster. Retarded timing can also affect power to the point that when tuning cars at times decreasing boost a few psi to allow for a little more advance timing increases horsepower, despite less boost.

BTW, what is your base timing set at? If you are running 12psi without an intercooler, my guess is that your timing is quite retarded to avoid detonation, if so try droping the boost by 2 psi and advance timing by 2 degree and take it for a test drive and see if it helps.

[yo2001]

I was only refering to the spool up of the turbo not the power output. less timing less power output but the turbo should spool faster. I guess on the stock liner ignition timing, the low timing will make the car sluggish.

 

I would also like to add the cam timing can affect the spool up. Specially with large N/A aftermarket cam.

[Clifton]

Exhaust flow spools the turbo. Less timing = less power = less exhaust = slower spool.

[Scottie-GNZ]

I think what Yo said was overlooked or misundertood. If he is referring to "spool up" as in spooling up the turbo at the starting line for a launch, then he is absolutely correct. That is a well known drag racing trick. Ever seen/heard some of the big HP turbo cars doing all that popping and farting at the starting line before a launch? What is happening (in most cases) is that the timing is being drastically retarded and the fuel is being leaned out to help spool the turbo quicker because there is not sufficient exhaust flow needed for those big turbos. The chip I use, Translator +, has the same feature. It senses the TPS open but 0 MPH and assumes the turbo is being spooled at the starting line and retards the timing and leans out the fuel mixture to help speed the spool up. Once it senses the car moving, it reverts to "normal" settings. You obviously do not want to do that for very long!

 

As for retarded timing = less power, I agree, BUT.... you do want to retard the timing as boost increases so you can have the capability of running more boost. More boost will always make more power than more timing.

 

As for the topic of the post, the problem is not the turbo. Several possible reasons have already been touched on, such as rich mixture at low RPMs/boost, exhaust leak between the head and turbo. If the problem is not resolved, it could actually be worse with a bigger turbo, especially if anything is done for more power on the turbine side.

[jtmny1999]

Thanks guys I will check my timing this weekend and see where it is at. My guess it prob is retarted because I can boost high without detonation

 

thanks again

[Afshin]

Ok everyone, I think that responses to post should relate to the case at hand. We are not discussing hypothetical scenario, someone posed a real question, the answers should follow suite. So for this set up, the comment “retarded timing improves spool up†while true in a vacuum, could unintentionally be misleading. I don’t think anyone would argue that the problem here could be advanced timing. As I explained earlier, if there is a timing issue in this case, it is because of excessive retardation.

Also while Scottie is almost always right and undoubtedly knows more than I do about turbo systems, I will have to respectfully disagree with him. Increase boost does not always result in more power over advanced timing. That statement is only true when timing is not excessively retarded such as max advance of 18 degree under boost and when the turbo is still in an efficient range of operation. As boost increases so does heat, when a turbo is being pushed beyond it’s limit where the efficiency drops (not too hard in a non-intercooled Z with a T3) power gain becomes marginal (and hence can be offset by timing power gains….), furthermore since so much heat is generated from the inefficiency of the turbo at higher boost, the timing has to be so retarded, that spark happens so late that combustion occurs when the piston is already too far on it’s way down, resulting in low combustion pressure and decrease power. And sticking with a stock l28et, this scenario can easily happen. Since in my line of work, references are a requirement and given that I’m pretending to work now, I will do the same:

 

Hugh MacInnes in his book: Turbochargers on page 68 gives an example of a VW engine, he said that as they advanced ignition too far, the exhaust cooled and boost and hp dropped, which is an example of too much advance not being good (again not the case in this post) but also said as total advance dropped below 26, the car gained boost BUT power decreased because of the retarded timing.

 

Graham Bell in forced induction performance tuning, page 72 claims “more boost and less spark advance OFTEN spell less hpâ€

Also based on personal experience, but without dyno quantification, I have felt the l28et running stronger at 12 psi than 14 psi with the amount of retardation needed to avoid detonation, this was with 91 octane and an intercooler.

Sorry about the long post, but I’m both bored and enjoying the topic at hand