HexRX

I know this has been discussed quite a few times, but after fixing and addressing most of the issues that were discussed, the spool still remains slow.

Current build:
1993' 1.6L running MS2PnP.
Compression tested yielded 190 across the board.
GT2560R with FM manifold and DP, 2.5" exhaust piping from the turbo back, straight through muffler and all mandrel bends.
Greddy type FV BOV
Turbosmart Boost T MBC
Rx7 Yellow Top injectors.
CX racing IC and piping, 2" off the turbo to a 2.5" to the Intercooler and all the way back to the TB.
Original 5 speed transmission with the 1.6 open diff.

Current issue:
I am hitting ~10psi @ 4k rpm. It turns out I had a few boost leaks and the wastegate actuator was a bit loose, so I fixed that and did a pull, overshot my boost target a bit but hit 10psi around 3500rpm; see photo 2.
So I readusted the MBC and went for another run, boost peaked at 4k rpm once again, see the photo 1.

The turbosmart MBC I have is a ball and spring type, which I was under the impression that it would help prevent the waste gate from cracking open by preventing air from reaching it until the target boost was hit.

Does anyone have suggestions as to why the delayed spool?
Running without the mbc, the peak boost @ 4k rpm.
I was thinking the gt2560r was a bit quicker to spool than this.

10psi @ 4k rpm; current situation



10psi @ 3.5k rpm; overboosted

squeegee

iTrader: (1)

Hey there, nice build! I'm going a similar direction so I hope that the 1.6 will spool better, especially with a nice BB turbo. What gear are you doing this in? If it's 4th (1:1) then it's definitely spooling slower than the pack in the spool data thread.

I'm really grasping at straws, but have you considered your BOV leaking? I've heard bad things about eBay units.

It seems like you have a pretty solid build, is it running funny in any other way?

HexRX

Thanks man.
Both logs were done in 4th gear and on the same street, going the same direction.

I sourced my BOV from Greddy in Irvine,CA and it doesn't seem to be leaking.

Other than the slow boost onset, its great! No issues I can attest to.
Idles perfect @ 850rpm & 14.7+- 0.2 AFR and is getting around 28mpg. There is no stumbling @ part throttle in boost or off.

squeegee

iTrader: (1)

no offense on the ebay comment, I just figured that's what you meant by "greddy type". I think cyotani had a similar setup, maybe he can give some insight

HexRX

Ah none taken, thanks for the advice though man.
Good luck with your build! Hopefully this isn't a characteristic of my setup and is just a weird leak or some ****.
Ill make sure to post the solutions I find.

Edit: Oh **** Cyotani and I have the same major, and both go to cal poly!

matthewdesigns

iTrader: (8)

I had a GT2560R on my 1.6 and I was hitting 17-18psi by 4K rpm. Hallman mbc and an adjustable wastegate rod.

Have you pressure tested the wastegate with compressed air to see at what pressure it is opening (directly to the can, no mbc in the middle)?

Have you checked the operation of the wastegate flapper to make sure it is not stuck? How about pulling the downpipe off to make sure it is closing all the way, or there are not any cracks in the turbine housing?

Have you driven the car strictly on wastegate, again no mbc in the middle? If so, how'd it look?

HexRX

I'll check the turbine housing tomorrow, but it should be fine as the turbo is only 3 weeks old.

The gate is opening and closing proper, and feels like it is shut solid. I will look though, I hadn't thought of that at all.

I was running wastegate pressure which was about 10psi, a little less. It had very similar spool characteristics, which is what lead me to get the 'ball and spring' type MBC. I was hoping that the wastegate was just opening under the exhaust pressure and leaking that pressure out past the turbine.

You were running that much psi by 4k?
See that is interesting, I over boosted (as showin in photo2) and was able to achieve my target boost a few hundred rpm sooner which makes me think that the MBC is faulty ?

mx5-kiwi

As a reference point Im running a gt2860rs on a semi log and getting 10+ at 3000 certainly 15+ by 4000.

You should be achieving better figures than that with the smaller turbo, definately mathewdesigns type figures...... Sadly I cant help any more than that, other peeps here know way more than i do....sounds like your on the right track though....

cyotani

iTrader: (8)

First check your blow off valve. I had issues with an ebay greddy rep bleading off boost when it shouldn't be. Add preload to adjustment if it is adjustable or replace it with a quality recirc valve.

Are you running a Megasquirt? If you are I'd advise ditching the MBC and running an EBC. With an EBC you can keep the wastegate 100% shut as long as possible and open it just in time to prevent to much overboost.

To see the true spool potential of your setup you can leave your wastegate unconnected (make sure you have overboost protection turned on and set to 12psi or so) and run your car WOT and data log. The RPM at 10 psi will be your absolute best spool with that set up. With a properly tuned EBC you should be able to get close to that.

A typical 7psi garrett wastegate cracks open and begins bleeding off boost around 3 psi. This hurts spool. Your MBC might delay that Waste gate crack open a psi or two but it is still bleeding off some boost well before your 10 PSI target.

Braineack

iTrader: (62)

1.6L and slow spool are ALWAYS in a sentence together.

youre running a 2.5" exhaust and MBC. Your experience seems right on par. the "revvy" cam of the 1.6L dictates a shitty spool and you're not doing yourself an favors by cracking the wastegate open and running a pea-shooter exhaust.

HexRX

Cyotani, the previous BOV I had was leaking, swapped it out with a real Greddy FV. Seems to be sealing very well.
I'll try the overboost datalog suggestion.

Braineack, yeah I've noticed quite the trend with the 1.6 and spool threads.
As for the peashooter, I have been searching for any data that can justify an additional 400$ drop into the car. The addition of .5" diameter to the exhaust would help flow, but to what extent. I guess I can do a bunch of data logs and post before and afters for future reference, unless you know of anyone who has done a good comparison?

Braineack

iTrader: (62)

look at dynos -- it's a lot. exact spool rpm matters little, but it will improve between the two.

shuiend

iTrader: (24)

This is why I went with a 3" exhaust on my MKTurbo setup, the price and noise difference is next to nothing, but the spool difference is well worth the larger exhaust.

cyotani

iTrader: (8)

I have a nice and quiet mandrel bent 3 in exhaust for sell =)

Less exhaust back pressure means more pressure differential across the turbine to drive it which means better spool. There is a point of diminishing returns tho. 3" seems to be sweet spot for this HP range.

aidandj

iTrader: (5)

I got like 400rpm of spool going from 2.7-3"

HexRX

Is this from downpipe back or turbo back?

aidandj

iTrader: (5)

I had 3"downpipe-2.7" exhaust. Now I have 3" all the way.

albumleaf

iTrader: (7)

Why aren't you using EBC with megasquirt? You're losing spool there for sure. It's not an a/b comparison but I'll hit overboost (14psi) at 3.5k in 4th easily on my setup, although I have a 2554r on a 1.6 (FMII kit, 2.5" FM exhaust).

mx5-kiwi

are you calling a 2.5" exhaust on a 1.6 litre motor a peashooter exhaust?

As a datapoint im running the 1600 with a bigger turbo and said "peashooter" exhaust with way better spool than he has, I doubt its the exhaust...and while I could be quite wrong, I personally doubt increasing 2.5" to 3" exhaust on a 1600 motor will make any discernable difference, all other things being equal....especially not to the the level the OP is looking for solutions to....


reading previous posts, I could well be wrong...seems hard to believe though.

Girz0r

iTrader: (1)

+1 Greddy FV, I <3 mine

My previous bov was a ebay knock off with o-ring seals that were busted. The mechanics of the ebay bov were not to my standard of what it 'should' be. Legit FV made tuning easier to manage.